How do I combine enemies together to reduce lag?

I want to combine enemies together to reduce lag cause lategame it just gets really slow, I want only enemies of the same type to combine and their health to be added onto eachother, that kinda stuff

Need more info there on what you mean be combine enemies

when enemies are overlapping one destroys itself and adds it's health onto another to reduce lag

Not sure what it has to do with reducing lag, but you can probably do this:

Enemy On collision with EnemyFamily

. Enemy health>EnemyFamily.health : 
.........Enemy add EnemyFamily.health to health, destroy EnemyFamily
. Else
.........EnemyFamily add Enemy.health to health, destroy Enemy