He is the once-great lord of the Almirian Empire, now a fiery citadel with Vanaduke the only living member left in it. He swears to guard his once-magnificent home and deal with any intruders. Most unfortunately for the Knights, Firestorm Citadel is the fortress blocking access to the Core, which they need to use to achieve victory and travel once again.
Vanaduke once determinedly led his empire against two opposing empires which had allied to crush Almire. Losing the war, Vanaduke fled into the mountains to seek assistance from a god. As he prayed, the god granted his wish to punish the empires, and he was transformed into a towering and fiery demonic being. As he returned with his hordes of undead, he laid waste to not only the opposing empires, but he unintentionally destroyed his own and its people, turning his beloved citizens into spirits.
With rage and guilt, he became bitter and even more malevolent, and swore to defend his home to make up for his past actions.
He sets up many traps and tests for the Knights as they make way into Firestorm Citadel, and eventually they confront him. Enraged, he vows that Almire's blood will never become un-purified by dogs like the Knights, and duels with them.
He summons lava rocks, monsters, and uses both his club and floating mask as weapons. In the end, he is destroyed by the Knights and drops, his body slowly disintegrating into dust, ending his rage, misery, and evil.
After his demise, wicked gremlin leader Herex takes control of Firestorm Citadel as his base of operations while preparing to breach the Core.
- For many years, Vanaduke was thought to be the main antagonist and final boss of Spiral Knights, seeing as he was the only boss fought in the 3rd Tier and was the biggest force menacing them. However, in newer updates, it is strongly implied that the true main antagonist and final boss is Herex, who has already been fought once after Vanaduke's death and escaped into the Core to carry out his own plans.