There isn't much debate over the hardest fight in the game. Even after Doom Eternal Ancient Gods Part 2 came out, the final boss was a cakewalk compared to the final fight in the Ancient Gods Part 1. By comparison, the Icon of Sin is a complete joke. The Mutated Seraphim has ended many Ultra-Nightmare runs for pros. Amateurs sitting on a stack of lives can lose them all just as easily.

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The boss requires a heavy dose of skill, tact, and preparation. That stands to reason when he's got a total of five phases and a limitless amount of tricks up his sleeve. Not to mention he adds and the platforming. If you're sick of losing on this boss, this guide will ensure that your last loss is the final defeat you'll ever have.


Get both Microwave Beam upgrades.

Get both Precision Bolt upgrades.

Use the Saving Throw, Air Control, and Chrono Strike base runes.

Use the Take Back support rune.

The mastery skills on the Plasma Rifle's Microwave Beam and the Heavy Cannon's Precision Bolt do area damage, and area damage is not imperative to this fight, but the upgrades absolutely are.

The Microwave Beam is required for two of the five stages. If the upgrades aren't ready, the odds of success are very low because the Slayer will be stuck in place for too long. No other mod is required, but the eyeballs from the turrets will make an appearance and this is the cheapest and fastest way to be rid of them is the Precision Bolt.

By this stage in the game, the player should have all of their suit upgrades. If not, feel free to play through the main campaign until this is maxed out; you'll need every advantage possible against the Mutated Seraphim.

This is a boss fight, so ditch the runes that kill trash mobs and trade them in for something else. There is a lot of platforming required during this fight, so the mobility runes should help a great deal.

Phase One - Fight At Range

Round one is pretty simple, shoot the Mutated Seraphim from range and dodge his orbs. Any weapon will do, but try to avoid using the Plasma Rifle or Ballista. Energy ammunition will be required for the following round.

If it becomes too difficult to dodge his orbs, recall that he raises two platforms but only shoots from one of them. You can evade his attacks by blocking them with the other platform.

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At no point during these phases should you attempt to use a melee attack against the Mutated Seraphim. He automatically casts a bubble around him if the Slayer gets too close that does a good amount of damage and pushed him away.

About halfway through, he will start to summon demons. Ignore them unless you need to chainsaw one for weapons or set them ablaze for armor. When he takes enough damage, he will automatically advance to the next stage.

Phase Two - Double Spirits

The Mutated Seraphim is invincible during this stage, so don't even try to damage him. He summons two Spirits and puts one into a Mancubus and another into a Prowler.

Immediately run behind the platform to block the Mancubus from attacking at range. Deal with the Prowler first. The Spirit will make him strong, but thankfully, ammunition is not an issue thanks two a few zombies that exist only to refill the Slayer's ammo with a Chainsaw strike. Use the Rocket Launcher or the Full Auto mode from the Combat Shotgun, then dispatch the Spirit with the Microwave Beam.

The other demon hits like a truck, but the Mancubus can be blocked with the platform, identical to how the Mutated Seraphim was defeated in phase one. Peek out, fire some shots, then duck back.

After both Spirits are dead, the Mutated Seraphim will glow orange and blue, you must finish him off with a glory kill. If not, be prepared to do the entire phase all over again.

Phase Three - Platforming

During phase three, the Mutated Seraphim will once again be invincible. Two more platforms will lift up and the ground will become electrified and poisoned. To add to the pandemonium, the platforms will take turns being covered in fire, two laser grids will activate and both back and forth, and Cacodemons will fly around.

This sounds like a lot to deal with all at once, and it is, but keep to this simple pattern: Leave a platform when it is on fire, dodging the grid as you jump, kill a Cacodemon, while on the new platform, and repeat.

The ground and flaming platforms are not instant death, so there is some license for error, but taking damage here makes the next two phases that much harder. After killing a few Cacodemons, the phase will automatically advance.

Phase Four - Dealing With Mobs And Shooting The Boss

Three kinds of demons will join the Mutated Seraphim at this point: Zombies, Eyeballs, and Makyr Drones. This sounds scary, but two of these actually help the Slayer more than they hurt him.

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Take a Chainsaw to the Zombies anytime it's on cooldown to top off ammo reserves. They spawn in twos, so feel free to set them on fire for armor as well. The Makyr Drones explode with ammo after taking a shot to the head with a Precision Bolt. The Eyeballs require two shots from the Precision Bolt, but it's worth it to have them die.

It's tempting to go through the portals and attack the Mutated Seraphim from the top, but this often doesn't work out. The Eyeballs will float up from the bottom and do a lot of damage in an area. The Mutated Seraphim himself will also teleport around, including on top of the Slayer if he is up top, and do that automatic melee damage from phase one.

The best plan of attack is to strike the Mutated Seraphim from the bottom when he comes into view. Whittle him down while stayed mostly focused on the adds. This keeps the population under control and keeps the Slayer topped off on health, armor, and ammo, which is critical to success in phase five.

Phase Five - The Same Room With Two Spirits

The Mutated Seraphim is immune again. The rest of the map is the same as phase four except for two Spirits, like in phase two. Instead of a Mancubus, one of the Spirits will be inside of a Pain Elemental.

Like in Phase One, use line of sight against the Pain Elemental and lure the Prowler away from the action. After killing the Prowler and the Spirit inside, deal with the Pain Elemental. In between, use the mobs to stock up on armor and ammo.

Most importantly, do not kill an enemy with a Spirit until you can kill the Spirit immediately afterward. Another host of the same kind of demon will spawn, effectively erasing any progress if this happens. Make sure you are full on energy ammo and won't be interrupted for a full Microwave Beam cast.

After these two Spirits are down, the fight will automatically end. Congratulations on making it through the toughest fight in the game!

NEXT: Doom Eternal: The Ancient Gods Part 2 - Ways It Sets Up A Sequel




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Andrew Robert Johns

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Hodey Johns is a writer for Game Rant based out of the Rocky Mountains in North Ogden, Utah. He's had a passion for video games and literature since he was a child growing up along the beaches of San Diego, California. As a graduate of Theology from Liberty University, he puts his experience with religion, philosophy, and debate into his work. His other interests include sports, smoking meats, and podcasting.

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