Wraith Stone

The Wraith Stone is a powerful item used by Amanda in both Tomb Raider Legend and Underworld. It was first found by Amanda in Peru, where it was the guardian of the resting place of the last Queen of Tiwanaku.

In Legend, Lara and Amanda escaped from the Unknown Entity. Amanda found the stone in a wall, finding out it was the monster's origin. So she got the stone, making the monster disappear. The stone is an artifact which can summon the entity (and also control it). Lara, after defeating Amanda, took the stone.

In Underworld, the doppelganger could get back the stone and deliver it to Amanda by Natla's orders. Later, Amanda used the stone to help Lara, killing the Thralls and Lara's doppelganger.

Powers

The stone has the power to unleash and control a powerful entity, who will obey the one who bear the stone. It can also be used to give the bearer the creature's powers, without needing to summon it, as Amanda didn't summon the entity in Underworld. Though powerful, the stone's powers are not unlimited. If it is used intensely and constantly, its powers will drain and temporarily end, needing time to recharge.