The Mysterious Assassin is a shadowy figure that is prominent throughout the Noga Kard. His true identity is unknown, and he is referred to by many vague monikers such as The Killer, The Scourge, and Evil Entity. Mysterious Assassin is used on multiple occasions, and as such, is the title most commonly assigned to him.

The Mysterious Assassin first shows up having kidnapped Princess Minava. He is fought and defeated by Du Sig. Later, at Du Sig and Mivana's wedding, he kills Minava's father, Coulagemo. He then declares war on the royal family, in which he kills Minava and Du Sig.

The Noga Kard also states that the corpse of the Assassin holds a being known as Xeed, a massive, two-headed monster that will destroy the world.