A Dark energy rune is a rune which can be made by players via the Dark energy altar, a rune altar created by Coraemalleia using a portion of the Dark energy core after stealing a part of the Ourania Altar. It can be used to cast Parasitical, a spell which releases part of the Dark energy core onto the opponent, draining their life force while adding to yours, and the spell Possession, which lets you control a target for 30 seconds, allowing you to avoid aggressive monsters, along with the spell Symbiote, which raises your Strength, Attack, Defense, Magic and Ranged by 20%. It can only be crafted (and used) upon completion of the Corporeal Lord quest. It is currently the most expensive rune that one can buy.