Where can it be found

South of Barbarian Assault mini-game by lighting a funeral pyre

Tactic

Turn on protect melee and finish it off. Try to have a prayer pot or two, just in case you take a while killing it. They are also weak against magic attacks.

Examine Message

He looks a tad upset.

Notes

This monster attacks you when you have any type of log in your inventory, with mangled bones, and click on the "Build pyre" spot along the edge of the lake in front of Otto the barbarian's hut.