First contact with a race called the Infelux.
Not much is known about them or their 'enemies' the Khoris. 3 Stooges refers to the 3 armor types found in battle.
Commando: Made famous at the Battle of Sparth Minor. If not for this unit they may never have taken that peninsula. 'Lighter' looking than the other types it seems to emphasize mobility than anything else. Any other special features are unknown.
Recon: Possibly the same type of armor as the Commando type. Field cloak seems to have a type of chameleon effect when in use, both visual and thermal. Unconfirmed.
Shock: Newest of the types. Armor seems to be more resistant to all types of projectile, especially armor explosives used by the Khoris. The design may be a response to what had happened at the end of the Battle at Sparth Minor. Heavier looking than the rest, rumor has it that it does not slow down or hamper mobility and increase strength considerably.
Major influences from Killzone, Resistance, HALO, Vanquish and other FPS I can't recall, because I have no original ideas.