Sentinel

You have mastered techniques to take advantage of every drop in any enemy's guard, gaining the following benefits.

• When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn.
• Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.
• When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.

name = 'Sentinel'
description = "***Feat: Sentinel.*** You have mastered techniques to take advantage of every drop in any enemy's guard."
def prereq(npc): return True
def apply(npc):
    npc.traits.append("***Sentinel.*** When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn. Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.")
    npc.reactions.append("***Sentinel.*** When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can make a melee weapon attack against the attacking creature.")