Withers

Sounds like a butler's name.

Come Withers, we have much to do!

Withers is a rather unique pet... He starts off almost as big as a regular Treant, but as time goes on he slowly shrinks down to the size of the Teldrassil Sproutling. However, if he is introduced to a source of water deep enough to swim in, he will regenerate back up to full size with the emote "Withers absorbs the water, growing back to full size."

Unique Features: This pet gradually grows smaller in size after being summoned and will regrow once it is brought to a source of water.

How to obtain it
Alliance: This pet can be obtained by completing the quest Remembrance of Auberdine. In order for this quest to be visible, players must first complete a series of chain quests in Darkshore. The quest hub for these quests can be found in Lor'Danel which is in northern Darkshore.

Horde: This pet can be purchased from Apothecary Furrows for 30 silver. Furrows can be found within a cave southeast of the Darkshore Alliance quest-hub Lor'Danel. If you are unable to locate him you may need to wait for him to respawn as the Alliance can kill him.

- All information taken directly from Warcraft Vanity.