New Mobs [quite a few so all in one post]

Tragnor: Short creature one block high on 2 flat footed legs very short that attacks by bending over and firing its quills that it has on its back at you drops quills that can be used as arrows (fires 2-5 quills at a time)

Fury: Large mob with a 4x4 block body with 8 arms and a huge eye hovers 1-2 blocks above ground and each arm can shoot beams of light at you which do lots of damage also short range attack by falling to the ground and causing a small earthquake will knock you back 1-3 blocks (BOSS)

Mocusa: Breed between a human and a spider with a spider lower body and a human torso but with spider like features can come in 2 types the Ranges type that spits poison at you and the melee type that stabs you with its pincers (fast moving)

Skilt: Looks kinda like a mix between a spider and a human human body bent forward with 4 very long and thin arms that whack at you drops skilt arms (used as spears because of the claws at end)
Blood worm: Red worm mob that lives in hot places can disappear into blocks to wait in ambush for the player to come by then jumping out and striking moves very fast (think silverfish)

Wraith: skeleton like create but can fly and only has an upper body can shoot red glowing orbs of magic at you that track you for 15 blocks then disapear or blocked by a block

Shamra: Balls of light that move in packs of 3-20 can fly have low health and average speed they die on contact with you but do half heart of damage and must be killed fast Highly aggressive drop glow stone dust

More coming soon

Awesome ideas. All unique and cool, though they seem very hard to code and/or model

Probaly so but i dont do coding thats up to you