The best Dungeons & Dragons monsters were the ones influenced by H.P. Lovecraft - the mind flayers, the grell, and to a lesser extent the aboleth.
The grell was a floating brain with a sharp beak, no eyes, and a mass of tentacles.
The Grell Shroom uses a brain-textured mold from a grell toy.
My dog Leona also makes an appearance in this picture: