Here are the following Creatures, Featured in this mod. Careful, for the Feature of the Creatures is divided into 4 sections, with more to come.
Eventually:tm: A fabric port will happen.

The Galenic.

Minds, The Unthinking Undead

A zombie with an oversized brain, enrages when hit.

I wonder if you could pop it...

Appears in warm biomes, such as Savannahs, drops the same things you'd expect for a zombie to drop. With some poisonous lead if Oreganized is installed.

Sinister, The Mirror, rirroM

A mass of silver tarnish, holding a mirror that reflects damage.

What if you hit the mass itself?

Appears in deep caves, drops the mud it's made of and Silver, if Oreganized is installed.

Beauty, The Beauty.

A lanky humanoid plant, seems to shrug off all attacks by parrying them.

What if you hit it while it's parrying another attack?

Appears in Lush caves, drops moss.

Machination, The Raging Machine.

A small, electrum golem(?) which attacks by kicking you. Can wind up a flying kick if far away enough.

And sometimes leaps directly into the lava below.

The NeverEnding.

All of these creatures and their features appear in the End.

Eeper, Whom dreams forever.

A distant relative of the creeper. Hops and scotches and marches directly towards you. Makes you fall asleep (slower speed, no jump, forced 3rd person) if it explodes.

Blitz, Whom does not retreat.

An elemental of. Something? Some thing. often leaps, dealing damage around itself and then dashes backwards or strafes.

MinedFlayer, Whom floats without worry.

A cosmic jellyfish, thinking of nothing. Floats around, floats to you if it spots you.

Doesn't deal any substantial damage, only disorienting you by rotating your camera and moving the player.

NoThing, Whom.

The description is empty.

Upon spotting a player, it shouts, revealing itself for a moment, then runs towards the player. It also becomes revealed upon getting hit or getting close to the target.

The Untamed.

Vertigo

A Sickened goat(?) equine(?) pig(?) deer(?).

Appears in dark forests, rarely in taigas. Charges towards the player as a regular walking enemy would. Rarely Sneezes(Spits?) at the player, knocking them back if caught in the attack cone and applying damage over time.

Canary

A Metallic lion(?) snake(?) bird(?) object(?).

Appears in very deep caves. Circles the player and tries to hit them with it's face plate (mask?). Inflicts delayed health loss, alongside simple melee damage.
The tail segments deal minimal damage to YOU, but the Canary takes full damage if those are hit.

The Friendful.

Fiend, a Fully Fiendish Fella.

Appears in Nether wastes, kicks blocks at the player while approaching to attack in close range. Sometimes may carry a skeleton.

Try moving to the left or right to avoid the punted blocks.