Bone Serpent Boss

The bone serpent is a new mid-game boss that can be summoned with a new item called the bone lure, which is crafted with 4 bones, 4 rotten flesh and a diamond in the middle of the crafting grid.

If a player drops the bone lure into a large enough lava pit in the overworld or the nether the bone serpent will appear with an emerging animation. The bone serpent will never leave the lava lake it was summoned in. 

The bone serpent has 2 attacks: the first is by moving up close to the player and bite them dealing 10 damage, the second is by opening it's mouth and firing a flaming skull at the player and deal 15 damage and set the player on fire.

Once defeated it will leave a 3X3 platform where it died, consisting of a gold block surrounded by bone blocks. On the platform will be bones, a new place-able item called the bone serpent skull which is purely decorative just as a trophy and the bone spear.

The bone spear is a melee and ranged weapon (like a trident) that cannot be crafted, it has 6 attack damage and 500 durability. It can be enchanted with: sharpness, looting, loyalty, smite, bane of arthropods, unbreaking and mending.

It also has 2 unique enchantments: charge has 3 levels and each one increases the damage dealt when a player attacks whilst sprinting into an enemy. Skull shot removes the ability to throw the bone spear but allows the player to shoot a skull when holding right click, it is mutually exclusive with loyalty.

(This idea literally came to me in a dream)