Thrall Artifact
From WikiRaider
The Thrall Artifact is found in Tomb Raider Underworld Beneath the Ashes chapter. It is not used in-game. It is a stone, rectangular-shaped, which has blue glowing letters. These letters says "Ohk Eshivar". After these two words are spoken, the speaker has total control about the thralls.
It is still unkown, but Lara could also control the doppelganger with the words. This may be revealed in Lara's Shadow
