Fabled Soulkius has practically the same effect as Infernity Knight, being able to revive himself from your graveyard for the same cost. However Fabled Soulkius has better stats. And can be revived anytime while in the graveyard, unlike Infernity Knight who can only be revived immediately after destruction.
Fabled monsters trigger their effects when they are discarded which already makes them a good compliment to Infernity cards who are all about having an empty hand. Infernity Knight can revive himself while simultaneously discarding Fabled monsters to trigger their effects.