Mass Effect 2
Aresh was among the group of subjects that had horrific, often lethal, experiments performed on them, primarily so the most important subject, Jack, would survive. Aresh, like most of the children, was sold to Cerberus by batarian pirates. He's one of the only other survivors of the mass breakout, and was mentally scarred by his experience to such an extent that he attempts to restart the facility, justifying that all the terrible things done to them must have been for a good reason, for some benefit.
During Jack's return to Pragia, Shepard and Jack fight their way past the Blood Pack mercenaries Aresh hired, led by the krogan Kureck. When they finally reach Aresh, he reveals to Jack and Shepard that he is rebuilding the Teltin Facility. Shepard can convince Jack to spare his life or allow her to kill him.
Mass Effect 3
If Aresh was spared, he survives the destruction of the Teltin Facility. Sometime later he takes up work and ends up on the colony of Elysium.
- Aresh's last name, Aghdashloo, is most likely a reference to Shohreh Aghdashloo, the actress who voiced Admiral Shala'Raan vas Tonbay.