The soul stone could save her spirit the eternal torment of being a plaything for the demons of the warp. The Laughing God may fight for her soul, but his victory was not, in any manner, guaranteed. That fear was the genesis of their arrangement, retrieve the ring for an reprieve from that fate.
The solitaire reached for the stone, hardly feeling guilt for this duplicity. How could the Laughing God, of all people, hold cheating against anyone, but as her fingers lay atop the stone, her vision fractured.