Delta was one of the Dark Ancients working with Epsilon to wipe out organic life in The Middle Kingdom. His primary role was manipulating the Orcs of the Urruk desert with his "Del" persona (in reality a stone golem coated in transmuted orc-flesh). It is unknown how Delta managed to maintain a continual supply of identical custom stone golems, as dark ancients burn through golem bodies much more quickly than they do Warforged.
As Del, Delta was responsible for sending Burg, Zil and Ing to assassinate Draven and also sent Hag and company to prevent Untor the Talker from retrieving the Ytarran artefact from the tram depot. Finally, he led Liz and some other orcs in an attack on the Northern Terminus, but was defeated by the party and killed, although not before taking over TR-4's body, effectively deleting the elderly transmuter's mind from existence.
It is possible that the Dark Ancients planned for Delta to lead a group of Orcs up the tunnel to Polaron to assist in Epsilon's takeover of the facility, but this is unclear.