The tree creature ("Dębostwór", or "Oak Critter", in the original Polish) is an entity that Geralt, Milva and Angoulême met in Caed Myrkvid. It looks similar to an oak tree, except of course being alive. Tree creatures are controlled by druids who use them to trap enemies.
The creature resembled a gigantic tree, a branching, ancient oak; perhaps it was an oak. But if so, it was a very unusual oak. Instead of standing somewhere in a clearing among fallen leaves and acorns, instead of letting squirrels scamper over it and linnets shit on it, this oak was marching briskly through the forest, stamping its sturdy roots steadily and waving its boughs. The stout trunk — or torso — of the monster had a diameter of more or less four yards, and the hollow gaping in it was probably not a hollow, but its maw, for it was snapping with a sound like the slamming of a heavy door.
pg. 261, The Tower of the Swallow (UK edition)
- It may be a possible reference to the original J.R.R. Tolkien's Ent or Huorn.