Mutations in Be The Final Boss are the difference between a minion army that clears waves and one that barely keeps up. Every unit you summon has a chance to spawn with a mutation that pumps its ATK and HP, and knowing which mutations exist, what they actually do, and how to see more of them will save you a lot of wasted Souls at the Summon Altar. This guide covers all three mutation tiers, the exact stat buffs attached to each, and the two methods available right now to tilt the odds in your favor.
What do mutations do in Be The Final Boss?
Mutations apply a flat percentage buff to both the ATK and HP stats of any unit that spawns with one. You'll spot a mutated unit immediately because the mutation name appears above its head and at the start of its name in the unit list. The trade-off is straightforward: mutated units cost more Souls to summon than their base versions, but the stat gains make that extra cost worthwhile at higher difficulty levels.
One thing mutations do not touch: active abilities, passive abilities, and range stats all stay exactly the same regardless of mutation tier. So a unit with a weak kit is still a unit with a weak kit, just a tankier and harder-hitting version of one.
Units can only carry one mutation at a time, and there is no manual way to apply or change a mutation after summoning. What you roll is what you get.
Cursed Moon doubles mutation odds
All mutation tiers and stat buffs
As of Update 1, there are three mutations in Be The Final Boss. Here is exactly what each one does:
Shiny is the entry-level mutation. A 30% bump across both stats is noticeable early on but starts to feel modest once you're pushing into harder content. Cursed doubles a unit's base ATK and HP, which is a meaningful jump. Demonic sits at the top with a 150% buff, making any unit that spawns with it significantly more powerful than anything below it.
How to increase mutation chances in Be The Final Boss?
Right now there are exactly two ways to improve your odds of rolling a mutated unit.
Cursed Moon weather event (free)
The Cursed Moon is a weather event that doubles the spawn chance for all three mutations while it's active. This is the only free-to-play method available. Timing your summons around Cursed Moon sessions is the most efficient way to farm Demonic units without spending anything beyond in-game resources.
Double Mutation Chance gamepass (paid)
The Double Mutation Chance gamepass costs 159 Robux from the in-game Shop. It provides the same 2x mutation buff as the Cursed Moon weather event, but the effect is permanent rather than tied to a timed event. If you're planning to summon a large number of units over many sessions, this gamepass stacks the odds consistently instead of requiring you to wait for the right weather.
Stacking both methods isn't confirmed to multiply the bonuses together, so treat each as a separate 2x source until the game clarifies the interaction.
What is the best mutation in Be The Final Boss?
Demonic is the best mutation available. A 150% buff to both ATK and HP on any unit is the highest multiplier in the game right now, and there's no competition from the other two tiers. The downside is that Demonic is also the hardest to get, so most players will spend the majority of their time working with Cursed units as a practical alternative.
Shiny units are worth keeping early in a run when you don't have better options, but once you're consistently rolling Cursed or Demonic variants on your core units, Shiny becomes filler.
For more Roblox guides covering idle games, mutation systems, and upgrade mechanics, the Roblox guides collection has everything organized by game. If mutation farming in similar games interests you, the Kick a Lucky Block mutations guide covers every tier and drop rate in detail, and the Cut Grass for Brainrots mutations guide breaks down Gold, Diamond, Rainbow, and Electro variants with full multiplier breakdowns.