Sepiks Prime

Sepiks Prime is a Fallen Servitor who is the boss of the Old Russia Strike mission Devil's Lair.

Offense
When Sepiks is close to a Guardian, it will fire a large beam of energy from its eye powerful enough to kill almost instantly.

Sepiks also teleports (like other Servitors), making him harder to target.

Vulnerabilities
Sepiks' eye is a critical hit spot. Firing on it from close range will deal more damage. Certain weapons, like fusion rifles, don't do critical damage when aimed at that spot.

Trivia

 * Fans have christened Sepiks with the nickname "Laser Face" -- a reference to a character from the popular Halo machinima web-series Red vs Blue, who for a short time, was in control of a Guilty Spark model.