History of Modular Sigma

Modular Sigma is a Taken Goblin and the companion of Modular Upsilon in the Fury mission. It projects an impenetrable shield that protects Upsilon, and it tries to repair Upsilon, so Upsilon is invincible while Sigma is active.

Fight

Deal with Sigma before Upsilon. Shoot its ocular, using cover while reloading. Once Sigma is down, Upsilon's ocular is open to damage. The fight also brings Taken reinforcements, which should be cleared before returning to Upsilon. Explosives work well when the pair roam near the Taken.