Corporal Beast

The Corporal Beast is a very difficult monster in Oldschool Runescape. When killing it, it will release a "core" monster that when standing still next to it or on it, will continuously damage you, healing the Corporal Beast. Most people use Emerald (e) bolts, or juggle it running 2x spaces away from it, to make sure they're not standing next to, or on the core.