A monster's pain state is an action frame used for that monster when being momentarily stunned by a damaging attack. Each monster type has a different probability of suffering this effect when hurt. This probability is called the monster's pain chance (from DeHackEd). The monster, when in pain from being hit by a projectile or shot, clawed or bitten, or punched or chainsawed, halts its movement or attack and displays its pain state sprite frame while usually giving a cry of pain, and then continues moving or possibly retaliates against its attacker.