Every time you pull a unit at the Summon Altar in Be The Final Boss, there is a chance it spawns with a mutation that raises its ATK and HP well above the base version. There are three of these mutations, and they get stronger and rarer as you go up the ladder. Knowing exactly what each one does, and how to tilt the odds in your favor, decides how much power you squeeze out of every summon.
Quick answer: Mutations roll randomly on summon and buff ATK and HP only. Shiny gives +30%, Cursed gives +100%, and Demonic gives +150%. To double your mutation odds, summon during Cursed Moon weather or buy the Double Mutation Chance gamepass for 159 Robux.
What each mutation does
A mutated unit carries its mutation label above its head and at the front of its name, so you can spot it the moment it appears on the altar. All three mutations scale the same two stats, ATK and HP, which also pushes up the unit’s overall power rating. They cost more Souls than the plain version, but the stat gain more than pays for the extra spend on a unit you actually plan to field.
| Mutation | ATK and HP buff | How it shows up |
|---|---|---|
| Shiny | +30% | “Shiny” label above the head and at the start of the name |
| Cursed | +100% | “Cursed” label above the head and at the start of the name |
| Demonic | +150% | “Demonic” label above the head and at the start of the name |
Demonic is the strongest and the hardest to land, so it sits at the top of what most players chase. Cursed is a strong middle option at double base stats, while Shiny is the most common and gives the smallest lift.
What mutations do not change
The buff is limited to raw ATK and HP. It does not touch a unit’s active or passive ability values, and it does not extend range. A Demonic ranged unit still fires at the same distance as its base version, so you are paying for durability and damage output, not for reach or improved skills.
As of Update 1, a unit can hold only one mutation at a time. There is no way to add or stack a second mutation onto a unit after it spawns, so whatever it rolls at summon is what it keeps.
How to increase your mutation chances
There are two ways to raise your odds, one free and one paid. Both give the same 2x boost to mutation chance, so the choice comes down to whether you want a temporary window or a permanent effect.
Cursed Moon weather (free): Summon at the altar while the Cursed Moon weather event is active. It doubles the chance of every mutation and is the only free method for improving your odds. Save your Souls and roll heavily during this window rather than spending them at random times.
Double Mutation Chance gamepass (159 Robux): Bought from the in-game Shop, this gamepass applies the same 2x mutation boost as Cursed Moon, but the effect is permanent. It stays active on every summon regardless of the current weather.
Note: The Altar Luck nodes in the Skill Tree only raise rarity luck. There is no Mutation Luck node, so skill points spent on Altar Luck will not improve your chance of rolling Shiny, Cursed, or Demonic.
Which mutation to target
Demonic is the best mutation to aim for because its +150% ATK and HP dwarfs the other two. It is also the rarest, so the realistic plan is to summon during Cursed Moon weather, hold onto any Cursed or Demonic units you land on the roles you need, and avoid burning Souls chasing a mutation that does not actually push you through a new wave. A base unit that fills a missing role still beats a mutated duplicate of a slot you already have covered.
