Twig

Twig appears as a dagger carefully shaped from a single piece of oak; the grain of the wood is plainly evident, as the craftsman who made it polished it carefully to bring a rich shine to it. Sized to fit the hands of an elf, the handle is wrapped in preserved leaves from the same oak tree that the wood was taken from, each leaf individually enchanted to keep it alive while rendering it stronger than leather.

The wood itself has been enchanted to remain strong and sharp, in spite of the passing of the many years since the blade was crafted.

Twig was crafted at the beginning of the War of Wood and Stone, when the elves and dwarves began their millenia-long feud; the elven mages who crafted it meant to make more like it, but they - and the secrets of creating more Twigs - were lost when the dwarves unleashed a burning geyser beneath their tower, destroying it.

Since that time, Twig has seen use in tasks both noble and fell; the Demon-King of Astalon fell when the dagger's magic destroyed his armor, leaving him open to be transfixed with an arrow of holy light, and the Seneschal of the Northern Wastes saw the great iron doors of the great fortress of the Knights of Truth fall as the blade's magic ate them away into a pile of rust.
Twig's last appearance was at the destruction of the Tower of the Dark Moon, where now there stands an immense tree, still decorated in places with the rubble of the tower.

Magical Properties:

Twig has two specific powers:
First, it will rust and corrode any metal the blade strikes, accelerating the aging of it a hundredfold. Any metal which does not corrode - such as gold - is immune to this effect.
Second, if an elf is slain with this weapon, it transmutes the elf's corpse into the base of a tree; for every year of the elf's life, the tree grows a handspan in height - it was this power that destroyed the Tower of the Dark Moon, when the head of the order within the Tower thought to see irony by sacrificing an elven mage with his own precious dagger.