LASO runs are the most challenging runs for Halo campaigns. A LASO run involves playing on Legendary difficulty with all Skulls turned on. If you complete a full run like this, you have absolutely mastered that Halo campaign. With such a challenging form present, is there any reward in Halo Infinite’s campaign for completing a LASO run?
Unfortunately, at least as of this writing, there is no reward for completing all of Halo Infinite’s campaign while doing LASO outside of an achievement. Doing that will earn you the Headmaster achievement and 100 Gamerscore. There is no in-game reward either in the campaign or multiplayer modes. The only content that transfers over to multiplayer is the cosmetics you earn from the Mjolnir Armory Lockers.
While some players might be disappointed that there is no reward for completing the hardest challenge in the game, LASO runs are completely voluntary. Unless you are trying to get every achievement in the game, there is no reason to attempt the feat, in all honesty. Because of this, we wouldn’t really recommend putting yourself through the headache unless you like challenging yourself. Completionists will have to deal with this headache if they want every achievement, though.