Talisman of the Wild

This mystic stone summons 1 Furbolg to fight for you. Lasts 180 seconds.

Also known as an Amulet of the Wind, this golden amulet is decorated with a scene portraying the night sky, with the constellation of the Bear clearly marked. At twilight, the shape of a bear-like creature can be clearly seen in place of the constellation.

The amulet can call forth a friendly furbolg as a fighting ally once per day. The furbolg is always the same each time, the actual creature having been entrapped within the amulet and forced to serve.

Source
Tyrande and Furion can find this in Brothers in Blood, chapter 5 of the Warcraft III night elf campaign, Eternity's End.