roper
A monster originally from Dungeons & Dragons, but also used in Tower of Druaga.
In the original D&D version, they masquerade as trees, and lash out with vines to drag adventurers to their doom.
The Japanese version, however, looks distinctly like a classic "tentacles monster", and as such, almost invariably appears in Japanese works as such a creature and for tentacle jokes.
It also appears more recently in some Monster Musume works, such as Monster Girl Encyclopedia, and as an evolution in Elona. Again, mostly as a tentacle monster reference.