many years ago occulto was human, but he spent much of his life trying to find ways of using magic to extend his life. eventually he found what he believed was a spell for immortality, but instead of making eternally young, it transformed him into a walking corpse.
Driven to the point of madness by his transformation, occulto vowed to become the most powerful warlock on Earth, using his immortal status to learn every spell, potion and incantation he could find. Eventually the magic drew him to Opal City where (like Captain Blood) he became convinced a way to lift his curse might exist.
And if it didn't, he'd have fun in the meantime by taking over.
Powers - occulto is capable of almost any spell, however due to his "undead" status, many require him to utilise the life force of others to complete them. his basic array of spells include teleportation, levitation, fire projection and invisibility. Each spell however lasts only as long as his concentration hold.
weakness - needing the life force of others to complete his spells means that he frequently is stopped simply by severing connection to his "volunteers". he also appears to have difficulty functioning in daylight which weakens him but doesn't kill him.