Miraculously, the Arbiter has survived Sunaion’s destruction, and the proud Sangheili warrior stands ready to help Osiris clear a path to the Guardian. This is fortunate, for Prometheans materialize en masse along this last broken road. Hold nothing back as you fight your way to the Guardian.
Recommended Loadout
Smaller arms will serve you well against the lowly Crawlers and Soldiers that first spawn, but you’ll want additional firepower to help you defeat the more powerful Prometheans that eventually appear. Plasma Casters, Fuel Rod Cannons, and Beam Rifles are all fantastic weapons to carry with you into this final battle on Sunaion. Ensure that your whole team is well equipped.
The broken road to the Guardian is filled with danger. Assist the Arbiter in eliminating the first few Crawlers that spawn as well as the Soldiers and Watchers that materialize afterward. Keep your distance, allowing the Arbiter to charge forward and eviscerate foes.
Legendary StrategyDon’t advance too far during this battle on Legendary difficulty. Take your time, keep to cover, and pick off Prometheans as you’re able. The large, square pillars near the entry point serve as effective cover until you’re able to advance to a safer position. |
Promethean forces continue to spawn as you push toward the Guardian, including multiple Soldier Captains armed with Splinter Turrets. Preserve your power weapons for now and use the building on the right to flank the Captains; you can do this from the ground level or soar up to its second-floor balcony via a propulsion lift 33. The balcony’s better, because you’ll find a Carbine and a Beam Rifle up there 34, along with a clear line of sight on the constructs below.
If you’re feeling frisky, leap to the toppled building ahead 35 and circle around its sloping balcony to discover two Fuel Rod Cannons and an Incineration Cannon on the building’s far side. This forward position is dangerous, so consider falling back to the previous Beam Rifle perch 34 after acquiring these valuable weapons.
Skull 10 of 13: Cowbell
After crossing the toppled building 35 and reaching the Incineration Cannon, drop to the street and advance toward the Guardian in the distance. 
Move to the very edge of the street 36, so that you’re as close to the Guardian as possible, and look down. Spy a small metal support beam below you and carefully drop onto it. Turn around after landing on the beam, and collect the little Skull behind you. Reaching this Skull is easiest before the Knights and Warden appear, and you can claim it on any difficulty. Snatch the Skull and then clamber back up to the action. 
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Promethean reinforcements arrive after the Captains fall, including more Soldiers, four Knights, and the fearsome Warden Eternal. Find a good spot to defend; the farther back, the better. The Beam Rifle perch 34 is an ideal location; use the Beam Rifle to score devastating headshots on the Warden. Just beware of the Soldier Captains’ and Knights’ barrages, along with the Warden’s lethal ranged attacks. Thrust to dodge incoming fire, and fall back behind one of the balcony’s support pillars whenever one of the Warden’s orbs comes your way.
Legendary StrategyEmpty the Beam Rifle on the Warden’s head the moment it spawns, falling back behind a support pillar as needed to avoid the Warden’s orbs. Thrust to one side to dodge the Warden’s eye beam, and when your Beam Rifle runs dry, use a Carbine to pick shots at the Warden’s head from afar. The balcony features a Covenant ammo crate, so you’ll never run out of Carbine ammo. Defeating the Warden in this manner takes time, but it’s one of the safest methods. Advancing to the forward Fuel Rod Cannons and Incendiary Cannon is suicide on Legendary. |
Let the Arbiter handle the melee fighting while Osiris spreads out to unload on the Prometheans from multiple angles. Keep your distance as you unleash your most powerful weaponry against Warden from afar. Keep an eye on the Warden throughout the battle and be especially careful to avoid its devastating ranged attacks.
The battle ends when the Warden finally falls. With the help of Spartan Palmer’s fancy Pelican flying, Fireteam Osiris manages to hitch a ride on the Guardian as it shifts into slipspace. Sunaion has fallen, and Osiris is back on Blue Team’s trail. Mission accomplished!
