Halo: Campaign Evolved warns that turning on difficulty modifiers blocks certain achievements. That warning is only half true. Mission completions still get written to your LASO progress while a maxed-out modifier preset is running, which means you can earn the MYTHIC achievement while taking almost no damage and never running out of ammo. The same trick clears the Mix Master achievement for a no-death Remixed run.
Quick answer: Collect all 17 LASO skulls, edit a modifier preset to Damage Resistance 2000% / Shield Recharge Rate 200% / Damage Modifier 300% / Melee Damage Modifier 300% / Bottomless Clip, then play each mission from the Play LASO playlist with that preset active. After each mission, check the MYTHIC tracker in the Xbox guide. If a mission fails to register, load The Pillar of Autumn with the preset set to None and grab the Speed Limit skull in the first area to re-enable progress.
What you need before the glitch works
The Play LASO option does not appear in the Campaign menu until you have found all 17 LASO skulls. There is no shortcut around this requirement, because the exploit itself starts from inside the LASO playlist. LASO here is a real mode, not an honor system. It stacks Legendary difficulty with 17 specific skulls and hands out MYTHIC once you complete the campaign with them all enabled.
Those 17 are part of the 39 hidden skulls in the game, spread three per mission across all 13 missions. The simplest path is to collect them on Easy during a normal story run, then come back for the glitch once Play LASO unlocks.
MYTHIC is worth 50 Gamerscore on Xbox and also unlocks as a Steam achievement or a Gold trophy on PS5.
Modifier preset values
The preset lives under the difficulty modifiers panel, reached by pressing X on the Select Difficulty screen. Each preset holds five adjustable traits. Set them to their extremes so nothing in the campaign can threaten you.
| Trait | Value |
|---|---|
| Damage Resistance | 2000% |
| Shield Recharge Rate | 200% |
| Damage Modifier | 300% |
| Melee Damage Modifier | 300% |
| Ammo | Bottomless Clip |
With these active, you take a fraction of normal damage, your shields snap back fast, your weapons hit for triple, and you never reload. On-screen text still tells you some achievements cannot be earned while modifiers are active. Ignore it for LASO progress.
Running the LASO glitch
The ten main missions carry the tracker to roughly 76%. The three bonus missions sit in their own menu and finish the run out to 100%.
How to confirm it worked
The achievement check and the progress tracker do not appear to read the same value, which is why the exploit works at all. Watch the MYTHIC entry in the Xbox guide after each mission. Clearing The Pillar of Autumn and grabbing the first skull moves the bar to 7%, which confirms progress is being recorded. Keep verifying after every mission rather than trusting the whole playlist at once.
Fix a stalled MYTHIC tracker
If a mission you just finished does not register in the tracker, you need to re-enable progress before moving on. The fix is a quick pass through the opening level with modifiers off.
Using the same trick for Mix Master
The maxed-out preset also carries over to the Remixed campaign. Load your no-death Remixed run with the same modifier values in place, and the Mix Master achievement for finishing Remixed without dying tracks the same way. Keep an eye on its progress in the Xbox guide, and use the Pillar of Autumn skull reset if a mission fails to register.
Note: In co-op, the game expects every Fireteam member to have presets set to None, so this is a solo workflow.
Will this get patched
The exploit runs directly against a design rule the studio documented, so it is a strong candidate for a fix. No official date for a patch that removes it has been confirmed. If you want the achievement the fast way, it is worth doing sooner rather than later, since an update could close the gap between the achievement check and the progress tracker at any time.
Worth keeping in perspective: a legitimate MYTHIC is one of the hardest things in modern Halo. Iron restarts the whole level on a solo death, Black Eye only recharges shields when you melee, Eye Patch removes auto-aim, Famine halves dropped ammo, and Fog kills your motion tracker. Stacking all 17 on Legendary makes a single bad grenade deep into a mission a genuine setback. Clearing that for real and clearing it with 2000% damage resistance both end with the same achievement, but they are not the same accomplishment.
