I would like some way of incorporating the Seven Deadly Sins as minibosses that have a chance of appearing on any non-boss stage. In my idea, they all move one tile per 8 seconds (except for Lust) and take 30 hits from Brother Bobby to be killed:
Pride: Sometimes fires four diagonal beams that need to hit a non-defensive baby twice to kill it. Also spawns a troll bomb, at a random tile occupied by a baby, that explodes like a Mulliboom attacking (which includes affecting an area around the baby).
Envy: Takes 27 hits instead of 30. Upon death, splits into 2 smaller copies on adjacent rows with one third of the splitting Envy's max health (9). Those 2 smaller copies can split again (3). If Envy is on the highest or lowest row, one of the copies will be on the same row.
Greed: Sometimes spawns a Hopper and shoots a spread of 3 tears (like every 5 seconds) when a baby is 3 tiles or less away from Greed. Each hit on a baby makes you lose 2 pennies, but only one penny drops on the ground.
Wrath: Throws a bomb (like every 5 seconds) at a baby if it is 3 tiles or less away from Wrath. Like a Mr. Shy, Wrath cannot deal contact damage.
Gluttony: Shoots 8 tears in both cardinal and diagonal directions. Can also shoot a Brimstone beam at a baby no matter the distance, but it only attempts to fire like once every 8 seconds and needs to charge for 4 seconds before firing the beam, a process which can be cancelled by freezing Gluttony or a charmed enemy attacking Gluttony.
Lust: Moves one tile every 2 seconds and poisons babies in contact.
Sloth: Acts like a Gurgle, but shoots more often and sometimes summons a Maggot.