The opportunity attack action is provoked by an enemy leaving an adjacent square without shifting or teleporting, or by an adjacent enemy using a ranged or area power. Like all opportunity actions, opportunity attacks cannot be provoked by forced movement.
Does crusher trigger Opportunity attack?
Yes, but only if the ability forces the enemy to move out of reach using their movement, action, or reaction. The rules state that only when the enemy uses their movement, action, or reaction to move out of your reach will they provoke an Opportunity Attack from you.
When does the Sentinel feat allow opportunity attacks to be provoked?
The Sentinel feat (PHB, p. 169-170) is specific on when it engages: Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.
What happens if you do not have the Sentinel feat?
The targeted entity does not have the Sentinel feat. It does not matter what caused the creature to make this attack in the first place so you can use Sentinel. It is important to note, however, that this attack granted by Sentinel using your reaction is not considered an Opportunity Attack.
What are the conditions for triggering a Sentinel?
The only conditions for triggering Sentinel are: The creature is within 5 feet of you. The creature makes an attack agains a target that isn’t you. The targeted entity does not have the Sentinel feat. It does not matter what caused the creature to make this attack in the first place so you can use Sentinel.
Can a creature within 5 feet of you provoke an opportunity attack?
Creatures within 5 feet of you provoke opportunity attacks from you even if they take the Disengage action before leaving your reach. Does this mean any creature at any time leaving your reach provokes an opportunity attack (including if they take Disengage?) If so, then abilities like the following would still trigger an Opportunity Attack:
