Currently there are only 6 bosses, but I'm planning to add more.
Bosses
Compsognathus
Drops: Compsognathus Claw and 2.500 experience points
Health: 100 hearts
Speed: A tiny bit slower than players sprinting
Attack: 7 hearts
Knockback: 0.6
Immune to: Fire, Arrows, Fall damage
Spawns: Any type of jungle biome
How to beat: Full enchanted netherite, shield, a few golden apples, and lots of space to run around
Note: Very dangerous!
Ender Cow
Drops: Ender Pearl and 1,500 experience points
Health: Very tanky, 175 hearts
Speed: Fast as a player walking
Attack: 3 hearts
Knockback: 0
Immune to: Fire, Arrows, Fall damage, Dragon's breath
Spawns: Any end biome, including main island
How to beat: continuously hit it until you get low, eat some food, and keep doing it.
Tropical Slime
Drops: Slime balls
Health: 50 hearts
Speed: Fast as a player walking
Attack: 4 hearts
Knockback: 4
Immune to: Fire, Arrows, Fall damage, Explosions
Spawns: Beach Biome
How to beat: continuously hit it until you get low, eat some food, and keep doing it.
Evil Nitwit
Drops: Emerald
Health: 90 hearts
Speed: A tiny bit slower than players sprinting
Attack: 7 hearts
Knockback: 0
Immune to: Nothing
Spawns: Plains
How to beat: Tower up
Villager King
Drops: Crown
Health: 90 hearts
Speed: A tiny bit slower than players sprinting
Attack: 4 hearts
Knockback: 0
Immune to: Nothing
Spawns: Plains
How to beat: Bow and Arrows
Items
Compsognathus Claw
Drops from: Compsognathus
Drop rate: 100
Crown
Drops from: Villager King
Drop rate: 100