Black Pudding
Found in subterranean complexes, where each creature of the number appearing may never encounter one another, the black pudding may serve to form a barrier across a particular passage or it may "hunt" by moving forward with a steady approach, catching a creature sleeping or one that is otherwise helpless. The pudding has no intelligence, though many continue to believe that the pudding's habit of making a pest of itself is done with conscious intent.
The monster attacks by forming a pseudopod from its body, which it can then whip at a defender with a likely chance of hitting. The pseudopod will then be absorbed again by the body, with time for a new one to form for its next attack. Only one pseudopod can be formed by the creature each round, but it may be on any side of the creature. The black pudding has no "back" so it cannot be flanked.
As well, the creature cannot be stunned, for though it can be attacked by normal weapons, no part of the body is made off balance by another part being attacked. This is true of all jellies, slimes and oozes.