Enemy
A creature whose goals oppose yours; the prerequisite for opportunity attacks, sneak attack triggers, and many hostile-target effects.
An enemy is a creature you treat as adversarial — one whose goals oppose yours in the current scene. Mechanically, "enemy" is the inverse of Ally.
Common rules that key off enemy status:
- Opportunity attacks trigger when an enemy moves out of your reach
- Sneak Attack applies when you have an ally adjacent to your target and no enemy adjacent to you (one of the qualifying conditions)
- Flanking (optional) requires an ally on the opposite side of an enemy from you
- Many spells specify "a creature hostile to you" or "an enemy you can see"
Determining enemy status: The DM is the arbiter. A creature with an Attitude of Hostile is automatically an enemy. An Indifferent creature is not an enemy unless something specific happens (an attack, a betrayal). A charmed creature is not an enemy of its charmer for the duration of the charm.
Mid-scene changes: A creature can become an enemy mid-combat (an ally turning on the party, a betrayed NPC) and likewise can stop being one (a defeated foe begging for mercy who is then spared). The DM signals these transitions.