you can comment your own interpretations of specific eternal monsters if you like

Monsters

Dumpling - Upon fart, shoots 2 bullets from its side (similar to when eternal pin spawns a trail of bullets when coming out the ground)
Scorching - Same function as eternal dumpling, but shoots out a ring of fire upon death
Skinling - Same function as eternal dumpling, but leaves a lingering poison cloud upon death
Scab - Passively shoots rings of 6 bullets while alive (similar to eternal suckers/spits)
Mortling - Spawns fart clouds in a short cross (4 directional farts) and bullets have aggressive homing
Tainted Dumpling - Upon fart, spawns several rock waves that travel outwards along with the usual bullets it spawns when farting
Fracture - Spews out short range homing bullets
Stillborn - Shoots 3 bullets instead of 1
Blind Bat - Bats will occassionally shoot a bullet at you
Echo Bat - Spawns a ring of 6 orbs along with its usual 3 orbs when attacking
Necromancer - Spawns eternal bonies
Swapper - Spawns a ring of 6 homing bullets upon swapping
Exorcist - Spawns eternal lil' haunts
Strifer - More accurate line-up with Isaac and shoots four consecutive triple shots when attacking
Screamer - Larger slowing aura
Canary - Larger technology laser, and shoots 4 split-shots upon hitting a surface
Foreigner - After breaking a rock, 3 eternal coal spiders will emerge from the spot
Graverobber - Less pickup spawns if anything has been stolen, and pickups have a chance to be degraded if possible
Splashy Long Legs - Takes less time standing still after putting its head on the ground and spawns more bullets
Sticky Long Legs - Chases you faster than usual while its head is down
Rag Creep - Quickly shoots many homing bullets in a single rapid burst
Split Rag Creep - Leaves damaging red creep after finishing its brimstone attack
Bloodworm - Spawns a few rock waves upon poking out of the ground and faster brimstone movement
Cell - Passively shoots bullets in random directions while fused. Shoots more if 4 of them are fused together
Barfy - Spawns an eternal spit while vomitting
Vessel - Spawns eternal level 2 charger upon farting
Corpse Eater - More health regen from killing enemies and a few homing bullets spawn along with the usual bullets after killing enemies
Carrion Rider - Same behavior as corpse eater, with an eternal bony saddling on top and occassionaly shooting. Leaves the eternal bony unmounted once the corpse eater is dead

Bosses

Raglich (not in restored collection, referring to the "Rag Lich" mod by Drarkyel)
- Spawns a few indestructible fires after dashing at Isaac. Fires distinguish on their own after some time.
- Fires spawned from the brimstone attck are indestructible by tears and distinguish on their own after some time.
- All rag creeps spawned during the fight are their eternal variants
- Moves faster when moving along the walls