EXTRA: Astral Stair Achievement in Vampire Survivors

Load up 'Inlaid Library' and make sure Inverse is turned on. If you've completed the base game, definitely just use Sigma, but any strong character will do. Consider also turning on Hyper and Hurry to speed this achievement up. Now, just play until you level up to level 80, which should happen somewhere in the 10-12 minute range in-game. Once you reach level 80, simply quit out of the run to unlock this achievement.