Malfera

"On candystripe legs the spiderman comes."

– The Cure

The Malfera is a stupid-looking horned elephant from the Dimension Of David Cook's Bad Acid Trips. This was introduced in X5: Temple of Death. Frank Mentzer realised "hey at least it's not a demon" so dumped it in the Companion Set; it is now a Mystara mainstay.

The malfera has crab-claws and fangs, using those on its victim. Two hits with the pincers, it draws you to the tentacles on its chest. Low-pH tentacles, to the tune of 2d6/round. It's also got "poison breath" which only works when it bites. But you do get +3 on your save before you croak.

As an extradimensional you need MAGIC to hurt a malfera. Natural abilities include Knock so, don't bother locking your door at night. And it sees through invisibility.

Its (toxic) "Dimension of Nightmares" didn't really take off in D&D; none of the later CM- or M- modules bother with it. It very likely inspired some aspects of Far Realm though.