Osiris (level)/Walkthrough

This is a walkthrough for the first level of Halo 5: Guardians, Osiris. It is written for play at Legendary and Heroic difficulty.

Level notes

 * Osiris is a rather narrow level, so cover is a must. You don't always have long sight lines here, so don't expect to easily stay back to snipe everything.
 * Forerunner weapons have been vastly improved over Halo 4's versions. Now many of them have greater range, better accuracy, and even tracking abilities.
 * The new Soldier enemies leap and teleport too fast to easily use the noob combo on them. The Boltshot is a better way to deal with them.
 * Unlike Elites but like Halo 3's Brutes, Soldiers' shields do not recharge when broken. Don't pursue one that flees when its shield is downed; he may lure you into am ambush.
 * Stay close to your team for firepower and revives, and order them to stick close to you. If any of them get downed, you can order a teammate to revive them, including through walls.
 * Never engage a Soldier with a Lightrifle while your shields are down. You will lose.
 * Watch out for glowing purple glares. That means more enemies are teleporting in.

Level Start

 * Locke: "Let's move. Vale, keep an ear on comms."
 * Vale: "Affirmative."
 * Locke: "Buck, Tanaka, pull security."
 * Tanaka: "On it."
 * Buck: "Aye."

Your landing area is no worry, as the debris from the ship you were running from wipes them out immediately. But before you leave the crash site so quickly, there's an option you need to know. To your right, on a ledge above the ship's debris, is a combat knife stabbed into the snow. If you shoot or melee it, it will light on fire and change many of the weapon caches from Forerunner weapons to human weapons. There are seven hidden knives in total, and shooting them all unlocks a hidden boss fight. If you want greater weapon selection, you can shoot the knife for more. But if you'd rather complete the level the canonical way, then ignore it and move on to the first area. Refer to here to read the location of all the knives.

The Crawler Assault

 * Locke: "Halsey and 'Mdama are holed up inside a Forerunner structure ahead. That's our target."
 * Vale: "So Halsey called us."
 * Locke: "She said there was something big out there, and gave Captain Lasky coordinates to find her."
 * Vale: "There must be something big."
 *  Buck: "Or one hell of a trap."

Ahead of you is a small valley with a few boulders for cover and several raised platforms. In there are a few Grunts, two Jackals with shields, an Elite Storm, and numerous Crawlers attacking them. The first area is all about headshots. Use your pistol for this area and conserve your battle rifle for now.

As soon as you enter, you'll see a Jackal fighting a Crawler. Headshot him before he turns to face you, then take out any Grunts and Crawlers near him. You'll mostly be limited to engaging from the right side of the boulder marking the "entrance", but you can climb up on top of it for some high ground. A second Jackal will be on a raised platform ahead of you; headshot him before he turns to face you. The only major danger you really have to look out for here is a Spirit dropship, which will fire some shots from its turret before flying away. If you see big blue projectiles heading towards you, fall back and wait for the dropship to leave.

It should be safe now to move up. A few more Grunts and possibly the Elite may be alive past the platforms, but they'll be distracted by the Crawlers. Take them out before headshotting the Crawlers. Be careful not too move up far, as the Crawlers' tracking shots can easily overwhelm you. Most will charge but one Crawler likes to hold position and snipe from the far end of the valley. Take it out if you see it being an annoyance.

Vale might say at this point that the area is clear, but it really isn't. More Crawlers will teleport in as you head up to the far end. They come from around a tall rock, so surprise them with a grenade and pick off the rest. After them, the area should be clear. There will be a brief Soldier encounter in the climb to the next area, but they don't fight, just flee. Before you leave, grab a new weapon to replace your likely near empty pistol. The Open Hand is a good replacement; it's hidden on a ledge to the left of where the Soldiers are seen. Climb up to the ledge and crouch walk over to nab it.

The Curving Valley

 * Locke: "Promethean! All sides."
 * Buck: "We could push right up the middle, but that'd be rough. Might want to consider flanking them."
 * Locke: "Move smart. Fire with a purpose."

Here's where things get tough. The new Promethean enemies, Soldiers, are going to be all over this area, and most of them are going to be armed with lightrifles. They tend to fire them in bursts of two, and on Legendary can easily knock you down with just four shots. Plus, they can teleport a short distance, though thankfully it's easier to track where they're going now. They're still fairly weak in this first level, and you'll have access to the Lightrifle and thus a reliable mid-range to long-range weapon. If a Soldier flashes yellow and their face turns orange, that means their shields are down and you can deliver a headshot. Using the squad commands can make finding them easier. Your teammates may have trouble against a healthy Soldier, but can easily finish off an unshielded one.

As soon as you climb up the hill and break through the ice wall, engage the Soldier on the other side. Two bursts from the Open Hand will strip his shields, then follow up with the lightrifle for a headshot. Then before you round the corner to the valley, look off the edge to your left. You should see a piece of Mission Intel and a carbine. Arm one of your teammates with it so they can a quick-shooting long range weapon.

As you round the corner, you'll immediately be greeted by two Soldiers with lightrifles and two Crawlers. Moving up will cause more to spawn and them to fall back, so you need to take them out now so they don't overwhelm you later. To take out the first Soldier, hug the right wall for cover and use the Open Hand-battle rifle combo on him. Then for the next one move to the left side to aim at him. Take out the Crawlers when you see them to make your aim easier.

As you move up and more enemies arrive, stick to the right side to take out Crawlers. Four more Soldiers will be on the outer edges of the valley, two on the left and two on the right. They each have lightrifles, so carefully use the Open Hand-battle rifle combo on each. If you run low on Open Hand ammo, offer it to a teammate and grab another boltshot; it'll only take an extra burst to drop shields. If you run out of battle rifle ammo, use the lightrifle instead. Clear out the right side first; its greater height means the Soldiers on it will be able to snipe you from farther in the map. Then clear out the left side. From a mid to long range distance, as close range will make them either leap away or toss grenades.

When they're cleared, that leaves one last part of the valley, a hill where four Soldiers are defending the entrance to the next area. The first two Prometheans tend to be more aggressive, so they can be lured out of cover. Either break the ice walls to the right of the valley or circle around the left platform to get in easier range for your Boltshot. The last two should then be flanked via the right ice wall path. While the Soldiers are distracted by your teammates, surprise them with an attack from the side. Sometimes you can even get an assassination on them this way. When Locke says the area is clear, then you've completed battling in the valley.

The Steep Hill
The next two rooms are transition areas, an introduction to the Artemis and a peek at the Kraken. But before you go, there is a weapon worth noting. On the edge of the cliff where the Kraken is spotted, two special scattershots, the Loathsome Thing, can be found. One is on the left and the other is on the right. It's a fast and powerful close-range weapon, especially when scoped in, so consider grabbing it and giving the other to a teammate. If you need to trade it to do so, there are weapons by the door where you entered the cave from the security station.