The Chronicles of Masteria [UPDATED 7/22/08]

It's a walking tree:

No, Ridley says:
"I taught countless mages during my heyday—from talented ones like Rafael, master of the mind; not so talented ones, like that bunch of ruffians who thought a staff was a walking stick; and the odd, most notably LeFay, who was in touch with a kind of chaos magic..." - Ridley

He's talking about people who wanted to be magicians but were so un-talented that they couldn't use their magic staffs for anything other than walking sticks.

I also don't really think that's a monster, it seems more like a trap, similar to the poison vents in El Nath dungeon or Gophers in Leafre Forest. Or, maybe it is a monster, just an invincible one that only appears for a second, like the Mirror Ghosts in the mansion. Just less annoying. I can actually see using those as a means to avoid HH's more deadly attacks.

EDIT:
Oh, and if the map that the HH is found on in these screenshots were the same as our current one, then it would have to have HH's tombstone on it. We can see in this screenshot that his tomb isn't visible, even though the treeline indicates he's against the edge of the map. So they either moved the Tombstone, or put him on a new map.