Phandelver + Storm King and beyond
Adonis is a mysterious figure from Quinys Forgedawn’s past who captured the party and offered her a chance to kill them and run away with him. She struggled with the decision but ultimately refused, but allowed him to escape after Edric Crestrun doggedly chased him down.
His whereabouts are currently unknown.
He left Quinys with some clues about her parents and a fancy rapier.
From there he , assisted by a dwarf named Fredegar, began to use his fell powers to raise undead utilizing an artifact he found. The undead he raised were either guardian mummies or docile zombies that retained whatever skills the had in life.
He used them to make equipment for some sort of invading Giant Army.
Not much else is known about the plan.
The heroes slew Adonis in the Barrow of Mad Martok.