xp boosters work up to lvl 27 iirc.
Obv they level very fast in the beginning (1 lvl each up to lvl 9 or 10)
So you won't be able to kill them before that point in order to lose xp and stop leveling.
And it's a tedious task to do it at such a low lvl having to do it after each run.
They do need to be alive ofc - otherwise they don't gain xp and there will be no surplus to the high lvls xp gain.
It's common practice to use ~4 xp boosters (there's a sweet spot but I don't rly know) once you are past lvl 93.
Iirc the calc isn't cumulative - they more boosters u add the less effective it gets.
They pros usually do 2/8 runs or entirely solo 1/8 if they don't have a playmate.
And yes, foh to clear cs is the fastest on low player count though I've seen a speedrunner (forgot who, need to check history to find it) who did solo cs p1 with a tri-elemental soso (blizz, hydra, nova) who did it faster than anything I'd seen b4.
His set up was this: Barb with D quests opens game, gives bo and leaves. Then soso quickly clears seals, finds es and loads the game to p8 placing 4 boosters spawning D before killing him.
Gl finding a commited team - it'd be a great thing to see happening in D2R
This post was edited by Sankturio on Jan 12 2026 02:15am