Shoggoth

''A shoggoth is an intelligent, gelatinous blob that can reshape itself at will. Created by an elder race as servants, the shoggoths rebelled long ago and slew their masters without pity. Since that time, they’ve lived in isolated or desolate regions, devouring whatever they encounter and absorbing its flesh into their own amorphous, shifting forms. Warlocks who make pacts with Elder Gods can summon smaller versions of shoggoths as their familiars.''