Boilers come as the ultimate repercussion of messing with xenomorphs and their genetics. Boilers are xenomorphs rendering incapable of evolving beyond their “drone” stage. And are in a constant, eternal state of suffering.
Example of a Boiler.

Boilers are Xenomorphs with incredibly poor genetic integrity. Not only are they stuck in an eternal state of torment they cant even survive a single attack. Boilers upon being harmed immediately explode, which in groups can be devastating.
Boilers can be weaponised by players. Should they be transported to be used as bombs on boss targets can make fights way easier, especially if they’re released in groups or swarms at that boss modded or not.
Boilers come as a result of -3.0 Genetic Integrity and less. Despite their condition they’ll actively remain just as hostile as a regular xenomorph and attempt to attack you without a care in the world.
Players can use boilers to their benefit in other ways rather than combat. Through rendering a queen incapable of producing proper workers and defenders and only boilers a player can make dealing with a hive much easier. Not only is crowd control much easier with them around, they can also be used to deal heavy damage to the queen herself should they cluster around her.
All strains have boilers. Nethermorph boilers follow a closer theme to the base Nethermorph and as a result their pustules are of a blue colouration akin to their blue acidic blood.