Soulstone Chamber

The Soulstone Chamber was built by the Horadric mage Zoltun Kulle. The Black Soulstone was kept in the chamber until the Nephalem entered and took the Black Soulstone after defeating Kulle.

In-game
The chamber can be found inside of the The Archives of Zoltun Kulle in Act II of Diablo III.

The portal leading to the chamber must be activated from 3 different realms (The Storm Halls, The Unknown Depths and the Realm of Shadow).