Sentinel 5e Guide

Sentinel 5e Guide

Dorin Darkchain hated Chult! The humidity made his plate mail very uncomfortable and he had to use his halberd weapon to hack his way through the undergrowth for seemingly every step. If it hadn’t been for the dark canopy, the duergar probably would have been blinded. Before leaving the Underdark, Darkchain hadn’t even known what a dinosaur was.

The sooner he could find the yuan-ti sorceress, the sooner he could leave this Laduguer-forsaken island!

What’s that?

His complaints were interrupted by a thunderous earthquake.

“Damn’t! Not again!”

He grounded the butt end of his polearm into the jungle floor and drove the point upwards as if he was expecting a charging boar.

The twin horns of a triceratops came burst through a grove of ferns and headed straight towards the gray dwarf. Standing only up to the beast’s knee, he drove the point of his polearm into the beast’s “shoulder”.

The impact shoved our anti-hero backward, but the seasoned battlemaster kept his footing.

The triceratops did not fare so well. It was nowhere near dead, but for a brief moment in time, it could not move forward. That was all the time Dorin Darkchain needed to give this overgrown lizard something to chew on. His halberd!

Sentinel 5e Guide: Bottomline

taken from Forgotten Realms Semantic Wiki

Sentinel is a feat that allows you to maximize your opportunity attacks and reduce your opponent’s movement to zero for 1 round.

How Does Sentinel Work?

Sentinel, when purchased as a feat, allows you to have the following benefits:

  • When an opponent is within 5 feet of you and attacks anyone other than you, you gain a melee weapon reaction attack (opportunity attack).
  • You get opportunity attacks on any creatures that leave your reach, regardless of whether they do it by Dash or Disengage.
  • If you hit an opponent with an opportunity attack, the opponent’s speed becomes 0 for the rest of its turn.

Who Can Use Sentinel?

Any character that can buy a feat in exchange for an ASI (ability score increase) can have Sentinel. This means that any character at 4th level and above can purchase Sentinel as a feat.

Is Sentinel Good?

Yes. Sentinel is so good that some DMs think it’s overpowered. Why?

As stated above in the “how it works” section, Sentinel creates opportunity attacks and allows you to capitalize on those opportunity attacks by reducing your opponent’s speed to zero.

Does reducing your opponent’s speed to zero take away your opponent’s ability to attack?

No, but in some situations it does.

Can you get an opportunity attack in every situation?

No, but some character builds are geared towards opportunity attacks. See the Sentinel Character Build below.

Sentinel Character Build: Darkchain the Duergar Battlemaster (Fighter 12)

Darkchain is a male Duergar fighter that has chosen the Battlemaster archetype. Here he is at 12th level:

Ability Strength Intelligence Wisdom Dexterity Constitution Charisma
Standard Sequence 15 14 13 12 10 8
Customized Sequence 15 10 12 8 14 13
Racial ASI +1   +1   +2  
4th + 6th Lvl. ASI +4          
Ability Scores Total 20 10 18 8 16 13
Ability Modifiers +5 +0 +4 -1 +3 +1


Lvl AC HP Move Weapon Equipment
12 22 100 25 +4 Halberd +3, +13/+9 Dam 1d10+9 (10-19), 3 Attacks/Action  +4 plate, +4 halberd, 2 +3 hand axes, 2 +1 daggers, 2 Healing Potions, 2 Message Earrings


Proficiency Source Type Ability Total Modifier
Smith’s tools Race Tool Strength +9
Stonecunning Race Skill Intelligence +8
Perception Class Skill Wisdom +5
Survival Class Skill Wisdom +5
Athletics Background Skill Strength +9
Intimidation Background Skill Strength +9
Mason’s tools Background Tool Strength +9
Carpenter’s tools Background Tool Strength +9
Herbalist’s kit Student of War Tool Wisdom +5

Fighter Features:

  • Dueling Fighting Style +2 to damage in melee
  • Second Wind
  • Action Surge
  • Extra Attack (3 attacks)
  • Know Your Enemy
  • 5 Superiority Dice
  • 9 Maneuvers
    • – Lunging Attack
    • – Pushing Attack
    • – Riposte
    • – Sweeping Attack
    • – Trip Attack
    • – Maneuvering Attack
    • – Menacing Attack

Speed: 25 ft/turn and no speed penalty for heavy armor

Darkvision: 120 ft

Poison: Advantage on poison saving throws and resistance on poison damage

Duergar Resilience: advantage on saving throws against illusions and against being charmed or paralyzed

Languages: Undercommon, Common and Dwarvish

Feats: Polearm Master and Sentinel

One of the reasons why I’m using Darkchain for this article is because Sentinel is a feat that works best when combined with Polearm Master feat. You’ll see why in the section below.

Buying 2 feats, however, can be expensive. Most characters only get 3 ASIs (ability score increases) by 11th level. Fighters, however, get 4 ASIs by 12th level. Those extra ASIs make fighter characters more willing to buy feats.

Fighters are also known for their multi-attack capabilities. They get more Extra Attacks than the other classes and can also use Action Surge to double their attacks. These increased multi-attack capabilities are very useful when used in conjunction with a Sentinel/Polearm Master combo, as you’ll see below.

Sentinel and the Polearm Master Feat

taken from Emkun

Sentinel combines especially well with the Polearm Master feat.

The Polearm Master feat is great with Sentinel for 2 reasons:

  • The Polearm Master feat creates opportunity attacks.
  • Most polearms have the reach property.

In addition to the opportunity attacks created by having the Sentinel feat, the Polearm Master feat creates opportunity attacks every time an opponent enters within your weapon’s reach. This means a Sentinel/Polearm Master combo creates opportunity attacks in the following situations:

  • An opponent enters within your weapon’s reach
  • An opponent is within 5 feet of you and attacks anyone other than you, you gain a melee weapon reaction attack (opportunity attack).
  • An opponent leaves your reach, regardless of whether they do it by Dash or Disengage.

If you hit an opponent in any one of these situations, their speed is reduced to zero.

The reach property is important if you want to maximize the benefits of reducing your opponent’s speed to zero.  Most polearms have a reach of 10 feet. Most opponents have a reach of 5 feet. Opportunity attacks are a reaction that can interrupt another creature’s turn, PHB p. 190.

This means that any creatures with a 5-foot reach (most creatures) who enter the 10-foot reach of most polearm wielders will not be able to make a melee attack first, regardless of who has the initiative, unless the polearm wielder has been surprised. If the polearm wielder has the Polearm Master feat, that attack is an opportunity attack and will not cost the wielder his or her action, including any attacks during that action. Furthermore, if the wielder has the Sentinel feat and hits with his or her attack, the victim will have its movement reduced to zero.

Can a victim with zero movement attack?

Yes, but only within the victim’s reach. This means that the user of the Sentinel/Polearm Master combo can take never be attacked by a melee opponent with a 5-foot reach, provided that the user scores a hit on every opportunity attack. To fully understand how this looks in an actual encounter, read the scenario below.

Darkchain vs the Triceratops

Darkchain, 12th-levelel duergar fighter (battlemaster), suddenly finds himself in the path of a charging triceratops.


13 10D12+30 95 50 ft 22 (+6) 9 (-1) 17 (+3) 2 (-4) 11 (+0) 5 (-3)
  • Size: Huge
  • Gore: reach 5 ft. +9 Attack Damage 24 (4d8 + 6) piercing
  • Stomp: reach 5 ft. +9 Attack Damage 22 (3d10 + 6) bludgeoning
  • Trampling Charge: Gore and Stomp combined from 20-foot movement

Challenge 5 (1.800 XP)

Round 1

taken from JurassicWorld fandom

The triceratops gets the initiative, especially because Dexterity is Darkchain’s dump stat. However, despite not having the initiative, Darkchain gets to attack first because he has a 10-foot reach and the triceratops has a 5-foot reach. Darkchain is wielding a +4 halberd with a 10-foot reach.

He hits the triceratops. Due to the Polearm Master feat, this attack is an opportunity attack. Due to the Sentinel feat, the successful opportunity attack reduces the triceratops’ speed to zero. The triceratops can attack during its turn, but only within a 5-foot reach because it has no movement.

As long as Darkchain maintains a 10-foot distance, he can continue to attack from a position of safety during the triceratops’ turn. Then he can use his movement to create another 5 feet of distance and wait for the triceratops to re-enter his reach. Then, Darkchain can repeat the whole cycle all over again next round.

That’s why DMs think Sentinel is overpowered!

As a DM, I might agree if that would be the only circumstance Darkchain could find himself in. Dungeons & Dragons, however, isn’t about only being able to operate in certain situations. The Sentinel/Polearm Master combo won’t do you any good against pit traps or trip wires. Nor will help solve puzzles or aid you in your social interactions.

Moreover, the Sentinel/Polearm Master combo isn’t equally applicable in all combat situations either, as you’ll see in my next scenario.

Darkchain vs the Tyrannosaurus Rex

Tyrannosaurus Rex
Image from forgotten realms fandom

Instead of a triceratops, Darkchain finds himself in combat with a charging Tyrannosaurus rex.

Tyrannosaurus Rex

13 13D12+52 136 50 ft 25 (+7) 10 (+0) 19 (+4) 2 (-4) 12 (+1) 9 (-1)
  • Bite: reach 10 ft. +10 Attack Damage 33 (4d12 + 7) piercing
  • Tail: reach 10 ft. +9 Attack Damage 20 (3d8 + 7) bludgeoning
  • Grappling Bite: DC 17
  • Multi-attack: 2x (1 bite + 1 tail)

Perception +4

Challenge 8 (3,900 XP)

The tyrannosaurs rex gets the initiative and charges into Darkchain’s 10-foot reach.

Round 1

Image from grobbulus fandom

T-Rex’s turn

The T-rex gives Darkchain an opportunity attack the moment he enters the duergar’s 10-foot reach. Darkchain hits the T-rex with his 1 opportunity attack, does damage and reduces the T-rex’s movement to zero.

Even though the T-rex has no movement, it still has a 10-foot reach and Darkchain is standing 10 feet away at the beginning of the T-rex’s turn. Therefore, the T-rex can attack normally and does so. It hits twice and damages Darkchain, but the duergar survives and the T-rex’s grappling bite attack is not successful.

Darkchain’s Turn

As a 12th-level fighter, Darkchain gets 3 attacks per turn, not counting opportunity attacks, bonus actions, and Action Surges.

Because he has the Polearm Master feat, he can attack once with the butt of his halberd as a bonus action. This will give him 4 attacks on his turn and 1 on the T-rex’s turn for a total of 5 for the round.

As a 12th-level fighter, Darkchain also gets 1 Action Surge. Should he use his Action Surge on the T-rex, he will get 2 actions and 2 bonus actions but no increase in the opportunity attacks that he had on the T-rex’s turn. This means that if Darkchain uses his Action Surge on the T-rex he will have 9 attacks total for the round: 1 opportunity attack, 6 multi-attacks for 2 actions, and 2 attacks with the butt end of his halberd for bonus actions.

Darkchain decides to save his Action Surge for more dangerous opponents and uses 1 action: 3 multi-attacks and 1 bonus action attack.

The duergar still has 25 feet of movement left on his turn. Here are his options:

  • He can retreat, but by leaving the T-rex’s reach he would provide the T-rex with an opportunity attack. Also, Darkchain only has a speed of 25 feet. The T-rex has a speed of 50 feet, so outrunning it is not happening. The duergar would, however, have a 25-foot head start because the T-rex’s speed had been reduced to zero for 1 turn.
  • He can move back a few feet, to create enough distance to force the T-rex to re-enter his 10-foot reach and allow another opportunity attack. The problem with that strategy, however, is that such a course would also grant the T-rex an opportunity attack because Darkchain would be leaving the dinosaur’s 10-foot reach.
  • He could use his Innate Magic ability as a duergar to make himself invisible and escape. He can’t do that this round because he’s used up all of his bonus actions. He can, however, use his action next round to Disengage and then use his bonus action to turn invisible. If he chooses this course, the T-rex would not get an opportunity attack on Darkchain but the dinosaur would get to attack first because it has the initiative and it has an equal reach to the duergar’s halberd.
  • He could not use any movement and not give the t-rex an opportunity attack. The t-rex would be able to attack the first next round, but then it would be Darkchain’s turn.

Reach Analysis for Sentinel

taken from

So, what effect did the Sentinel/Polearm Master combo have on the T-rex?

Sentinel: It allowed Darkchain to use his 1 opportunity attack for the 1st round of combat and reduced the T-rex’s speed to allow for additional options for the duergar to choose from during the 1st round of combat. From the 2nd onward, it had no effect.

Should the T-rex try to Disengage in later rounds, Darkchain would be allowed to use Sentinel features again.

Polearm Master: It gave Darkchain 1 opportunity attack for the 1st round of combat. Without the Polearm Master feat, there would have been no opportunity attack in the 1st round. Without an opportunity attack, there would have been no use of Sentinel features in the 1st round. There was only an opportunity attack available in the 1st round.

The Polearm Master feat allowed Darkchain to attack with the butt of his halberd as a bonus action in Round 1, giving him 1 additional attack that he otherwise would not have had.

During Round 2 and all future rounds of the fight, this particular feature of the Polearm Master feat allows him to attack with his bonus action once per round throughout the entire fight.

Now if Darkchain were to try to use his Sentinel/Polearm combo on red dragon, the monster would still be able to use its breath to bake the duergar. This and many other situations are why I don’t think the Sentinel feat is overpowered.

The Battle of the Coffins

Boris and Natasha are a nice vampire couple. Nice, meaning that they are late risers with a very active nightlife. Most warm-blooded demi-humans and humanoids don’t like them because of the couple’s bloodsucking ways, but among undead society, they are the talk of the town. Their stats are identical:


taken from Angie Bell on Pinterest
16 17d8+68 144 30 ft 18 (+4) 18 (+4) 18 (+4) 17 (+3) 15 (+2) 18 (+4)
  • Multi-attack: 2x (2 strikes or 1 strike + 1 bite)
  • Unarmed Strike: reach 5 ft. +9 Attack Damage 20 (1d8 + 4) bludgeoning
  • Grapple: Can be used instead of damage on a successful strike DC18. Can bite only during a successful grapple.
  • Bite: reach 5 ft. +9 Attack Damage (1d6 + 4) piercing + (3d6) necrotic
  • Vampires regain hit points equal to any necrotic damage inflicted.
  • 3 Legendary Actions: Move, Bite, Strike
  • Spider Climb
  • Charm DC 17
  • Children of the Night (Summon 3d6 wolves or 2d4 bat swarms)
  • Shapechanger: tiny bat or medium mist cloud
  • Misty Escape
  • Regeneration: 20 hit points at the start of its next turn
  • Passive Perception 17 Perception +7 Stealth +7
  • Damage Resistance: Necrotic, Nonmagical Bludgeoning/Piercing/Slashing
  • Sunlight Hypersensitivity
  • Challenge 13 (10,000 XP)

Darkchain is not a saint, but even he does not approve of their lifestyle and decides to put an end to their nightlife. He manages to find out the location of their resting place and decides to lay an ambush for them.

He’ll let them go out for one last night’s hunting and wait for them in the coffin room. Yes, they had a few guards, but his duergar invisibility enabled him to bypass their sentries unnoticed.

Note: The battle map below shows the following tokens:

B= Boris

N = Natasha

CC= two coffins

Gray square = Darkchain

Round 1

image from David Blanc

The double doors open and the vampire pair enters the coffin room. Because of their exceptional Passive Perception, they sense a threat just as they enter the room and instinctively fan out. They have the initiative. Darkchain is standing 9 feet away from each of them, as seen on the battle map above. Despite the vampires getting the initiative, Darkchain’s 10-foot reach is longer than the vampires’ 5-foot reach, so he gets to attack first.

Vampires’ Turn

As they are entering the doorway, however, they are also entering within reach of Darkchain’s halberd, giving him an opportunity attack due to his Polearm Master feat. Using the Swing Maneuver and spending 1 of his 5 Superiority Dice, the Battlemaster rakes the blade of his halberd across the thighs of the vampire couple with one mighty swing, doing 17 points of damage to each of them. Due to his Sentinel feat, both undead have their movement reduced to zero.

The vampires attempt to strike and bite to the best of their ability, but it is futile. With their movement destroyed, they just can’t close the 9 feet of distance to touch the laughing duergar Battlemaster.

Darkchain’s Turn

Darkchain decides to save his Action Surge for when he needs it, so he only gets 3 attacks with his halberd’s blade and 1 bonus action attack with his halberd’s butt end. He focuses all 4 of his attacks on Natasha. He hits with all 4 attacks, doing a total of 65 points of damage, not including the 17 points from the opportunity attack. Natasha screams in paint and fear.

He uses his movement to step 4 feet back, placing 13 feet of distance between himself and the 2 vampires. In tandem with his movement, the Battlemaster taunts Boris,

“What’s the matter? Can’t you protect your wife?”

He is hoping that they will move within range of his halberd again. Darkchain’s turn is over.

Normally vampires would be able to use Legendary Actions to move into Darkchain’s space and attack him on his own turn. However, because Darkchain has used his Sentinel feat, they can not move and attack him with their Legendary Action because they cannot move until their next turn.

As a bonus action, Natasha yells, “Help me! Help me!”

Boris orders, “Guards, protect your Mistress!”

At the end of Round 1, Boris is down to 127 hit points and Natasha is down to 62 hit points.

Round 2

Image from grobbulus fandom

At the beginning of the 2nd round, both vampires regenerate up to 20 points of damage, completely healing Boris.

Darkchain’s taunt wasn’t motivated by ego. He wanted to provoke Boris to attack with everything the vampire has. Normally they could use their Legendary Action to close the distance to Darkchain without provoking an opportunity attack. The problem is that they can’t do that until their opponent Darkchain completes his turn and their turn is before Darkchain’s turn.

Vampires’ Turn

Darkchain’s taunt works. Natasha is smart and takes the Ready action but not Boris. Rather, her husband decides to use his movement and attack at the beginning of his turn.

Darkchain’s long reach still allows him to attack first on Boris’s turn. Furthermore, because Boris is again entering Darkchain’s reach, Darkchain has an opportunity attack and can again use his Sentinel feat.

Darkchain’s opportunity attack is successful and again the vampire’s speed is reduced to zero, all on Boris’s turn. Darkchain laughs,

“Boris, it’s time to say goodbye to your wife.”

Natasha normally would flee, but her resting place is the room in which the fight is happening and dawn will soon arrive. Her best chance is to wait and attack on Darkchain’s turn.

Even though Natasha isn’t attacking yet, she does speak while she waits,

“Guards, hurry!”

As Darkchain gets within striking distance, he replies,

“They’re not coming. My friends have seen to that.”

Darkchain’s Turn

Darkchain slowly but deliberately strides over to Natasha.

Even though Natasha has taken the ready action, the DM rules that Darkchain gets to make one of his attacks first because of his reach advantage. It hits and does 16 damages, but it’s not an opportunity attack.

Now Natasha can make her first of two attacks. She misses and Darkchain spends another 1 of his Superiority Dice to perform a Riposte Maneuver off Natasha’s failed attack. Darkchain’s Riposte Maneuver is an opportunity attack and again, Natasha’s speed is reduced to zero dur to his use of the Sentinel feat. His Riposte does 20 points of damage.

Darkchain has 2 attacks left plus 1 bonus action attack. With those 3 attacks combined, he does another 55 points of damage, 91 points of damage for the round total. This reduces Natasha to -11 hit points before she can use her Legendary Action or even her second attack. Natasha’s body turns into a cloud of mist. She tries to return to her coffin but even in mist form, she can’t move until her next turn, thanks to the Sentinel feat.

Darkchain’s turn is now over and Boris can now use his Legendary Action. Boris cannot move, however, and can only use his Legendary Action to summon some bat swarms. In his heart, however, the vampire knows that the battle is lost.


Question: What is the maximum number of times you can use Sentinel in one round?

Answer: 4, if you base the answer on PHB rules. You can only use Sentinel to take away movement on an opportunity attack. Opportunity attacks are reactions. You are only allowed 2 reactions per round. With the Swing Attack maneuver, you can attack 2 opponents with 1 attack. If both your reactions use the Swing Attack maneuver, you can attack 4 opponents with 2 reactions. If you hit all 4, you can use the Sentinel feat to reduce their movement to zero, all within the same round.

Question: Why do you say 2 reactions per round? I thought it was 1 reaction per round?

Answer: Once you have a reaction, you can’t have another one until your next turn. However, if your opponent takes his or her turn before you, you can have a reaction on your opponent’s turn. Then when your turn comes, you might be able to have a second reaction depending on what any one of your opponents does during your turn.

Therefore, it is one reaction per turn, not per round. Every round has at least 2 turns: your side’s turns and the turn(s) of your opponent(s).

Question: Can Haste Spell increase my opportunity attack maximum?

Answer: No. Your character’s number of attacks per round has nothing to do with the number of reactions that the character can have per round.

Question: Besides Polearm Master, what other feats and class features combine well with Sentinel?

Answer: Anything that creates opportunity attacks will create more opportunities to use Sentinel. As mentioned in the vampire battle, fighter Battlemaster subclass maneuvers like Swing maneuver and Riposte maneuver can be used to maximize or created opportunity attacks.

The Mage Slayer feat can create opportunity attacks but it does not combine well with Sentinel. The reason is that wizards and other casters are primarily long-range fighters. There’s no point in reducing a wizard’s movement to zero if they can kill from 100 feet away with a Fireball.

Question: What tactics and opponents are Sentinel best for?

Answer: Sentinel works best against opponents who like to melee and not as well against opponents that have good ranged attacks.
The ability to take away an opponent’s movement is great for parties that like to pile up on 1 Big Bad. Even if the Big Bad has ranged attacks and spells, taking away the Big Bad’s movement is great for establishing control of the battlespace.


Sentinel feat is made for masters of the counterattack. Provided that you have an opportunity attack, you can use Sentinel to take away your opponent’s movement for the rest of his or her turn. If you can do that, there are many tactical advantages for those who are clever.

Darkchain was a good example for Sentinel because he doesn’t depend on Speed or Dexterity: his Speed is 5 feet slower than most humans, 25 feet, and his Dexterity is 8. Regardless, he was still able to get opportunity attacks and use Sentinel in different situations: opponents entering his reach with his Polearm Master feat and him scoring with a Riposte Attack with his Battlemaster maneuver. His ability to take away an opponent’s movement could be used to maximize his reach as he did with the triceratops or to separate his opponents and use Defeat in Detail as he did with the vampires.

Some DMs think that the Sentinel feat is overpowered. I disagree. Martial classes like fighters have to compete with caster classes and monsters that have ridiculous abilities. The Sentinel feat simply represents what a mid to high-tier martial class character like Dorin Darkchain can do.

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