In the Peru level, Lara will find the body or the statue of the queen an a fragment of the Excalibur. It was aprisionated in the Wraith Stone by Armanda Evert and releasd to by Armanda Evert The full extent of it's powers include throwing fireballs, teleporting and merging with other beings - one who obtains the stone can have complete control of the entity.
In Bolivia Redux Amanda will merge with the creature to form the stone.
After the events of Legend, Lara keeps the Wraith Stone, but it is stolen from her by her doppelganger and given back to Amanda. Amanda later uses it to help Lara fight Thralls in the Arctic Circle level as Lara goes to find her mother.
Lara first encountered it in some ruins near Paraíso, Peru where it slaughtered most of Lara's colleagues.