Boss 1: Aquamentus
On one of two large islands in the center of Lake Hylia, Hyrule’s largest central inland body of water, sits an ancient tree. A tree that somehow feels like it was once a living creature, the surrounding air reeking of a deathly stench. Millenia ago, the tree was converted into an underground complex and entrance to the underworld by a tribe of ancient druids that worshipped one of the oldest demon gods: An aquatic dragon-like beast bestowed with the name Aquamentus. Though it is yet to be known why, carvings resembling that of an eagle are found all over the complex; a complicated labyrinth of cramped, crudely dug-out tunnels, with the entangling roots from the tree above creeping down below. Aquamentus is one of the oldest of the 6 demon gods, its large equine-like body emaciated and worn, its joints cracking, splitting and rattling as it moves. Its seemingly dilapidated body shouldn't let a warrior's guard down however, as its size and abilities are formidable. Adorned with a large horn near the top of its skull, Aquamentus has the ability to emit lightning from it as a conductor, the bolts of which can fatally burn and char any living thing. Ganon's possession of the creature has given it but one purpose, to defend the Triforce shard with its life.
One of the elderly demon's offspring had also been captured and utilized by Ganon as a guard for another Triforce shard, found in a secretive tomb underneath an abandoned fairy pool in western Hyrule.