This battleaxe is found on embedded in the Gulthias Tree on Yester Hill in Curse of Strahd.
it's handle is carved with leaves and vines, and it weighs half as much as a normal battleaxe.
When the axe hits a plant or a plant creature, the target takes an extra 1d8 slashing damage.
When a creature that is not good aligned picks up the axe, it sprouts thorns and whenever they make and attack with it that pricks the user for 1 piercing damage (magical) after the attack.
Proficiency with a battleaxe allows you to add your proficiency bonus to the attack roll for any attack you make with it.