Unlike other legendary gem, it can only be inserted in the helm slot. Doing also gives you a special transmog. (Obviously a reference to the Diablo 1 ending that the hero plunged the soulstone into his own head.) Its AoE damage is decent. However, the proc rate is quite low it is on a long timer. Also, every time it procs, the player character is stunned briefly.
- Check the corpses in Tristam for hints (optional)
- Find the Black Mushroom in labyrinth level 9 (0:36) and get the Rotten Mushroom.
- With the Rotten Mushroom in your inventory, go back to Tristram, then go east and find Adria's hut. Click the cauldron to get the Witch's Brew.
- Go back to Tristram and click on the corpses one by one according to the hints. Finally Griswold's corpse drops the plan for Wirt's Leg.
- Learn the plan at the blacksmith. Craft the Wirt's Leg (it is a mace) and you get the new transmog.
- Salvage the Wirt's Leg to get Map of the Stars.
- Go to Tristam, follow the east road and find the corpses of three cows.
- Click the corpses in order according to the hint of the Map of the Stars: 2, 1, 3: which means middle, left, then right. The entrance to Abandoned Farmstead appears.
- Enter the Abandoned Farmstead. A chest is in the center of the area containing the Royal Calf pet. Right click the Royal Calf pet to add it to your pet collections.