An Omni soulstone is an item created by combining the Zamorakian soulstone, Saradominist soulstone, Bandosian soulstone, and Armadylean soulstone. This can only be done when in close proximity to an altar just east of the rope exit in the God Wars Dungeon.
The Omni soulstone allows the player to preserve their killcount of the hard mode versions of K'ril Tsutsaroth, Commander Zilyana, General Graardor, and Kree'arra, instead of draining away when players leave the God Wars Dungeon. This allows for players to go straight into the boss room if they have the required killcount without having to regain the killcount from the minions of that god. The normal versions of the four bosses also count, but five normal kills are required for one charge of the soulstone.
Charges in the Omni soulstone will be used and lost upon opening the respective boss door. Kills gained from minions are used before those in the soulstone.