Annihilate Those Who Dare Disturb the Peace of the Forest!
The forest guardian is a monster that appears in the forests in time of desperation, ready to swing the branch of dead trees at intruders until they fall dead. In addition they have mechanics similar to flesh golems, where various damage type affect them differently, and the most fun mechanic in my eyes, to reflect all fire damage. Next time a pyromancer approaches them, they might think twice about it.
Adding more forest type monsters is a fun thing to do, It goes especially well if you run a certain adventure which contains a lot of dinosaurs.
I actually created 3 new monsters, this one as well as the Blightforged and Corrosive Golem, you can find all of these for Free on Patreon.