Arena Trap prevents all foes from fleeing (includingTeleport) or switching out as long as the user remains in battle.
Pokemon rendered immune to type attacks are immune to Arena Trap. This includes typePokemon, Pokemon with Levitate, Pokemon holding anAir Balloon, and Pokemon affected by Magnet Rise or Telekinesis. Likewise, if a Pokemon normally immune to type attacks is made vulnerable, they will be affected; if the Pokemon is under the effect ofGravity, Smack Down, a move that negates or replaces Levitate (such asGastro Acid or Simple Beam), type change effects that remove type (such as Soak, Conversion, Camouflage, or Color Change), or a held Iron Ball, it will be unable to escape.
Using Baton Pass, U-turn, Volt Switch, or Parting Shot will still cause the Pokemon to switch out. Holding a Shed Shell allows the Pokemon to switch out, but not flee or Teleport. Having the Ability Run Away or holding a Smoke Ball allows the Pokemon to flee or Teleport, but not switch.
If a wild Pokemon has Arena Trap and the player’s Pokemon faints, if the player attempts to flee instead of sending out another Pokemon, they are unaffected by Arena Trap.
Arena Trap does not affect allies.
Ghost Pokemon are now immune to Arena Trap.
Outside of battle
From Pokemon Emerald onwards, if a Pokemon with Arena Trap is leading the party, then the wild Pokemon encounter rate is increased to 200%. It shares this trait with Illuminate.
Pokemon with Arena Trap