In his right hand is the Candle Whos Light is Shadow. In his right he holds a dead star. His left hands are stained with the blood of Am Dhaegar. -Invocation of Zalgo
Zalgo is depicted as a jet-skinned knight in silver armor surrounded by a corona of black lightning.
However, his true form is much more horrific. He is described as having seven mouths speaking in six foul tongues, the seventh singing the song that will end the world, and four arms holding a Black Hole and a candle that sheds darkness rather than light. Am Dhaegar may have been an ancient city, another entity like himself, or anything else, up to and including an entire universe. He is also described as an amorphous, eyeless being. As Zalgo is malevolent chaos incarnate, both descriptions may be true.
Zalgo lives in a palace of tortured glass, served by legions of monsters forged from the tears of the undead, and each one clad in armor carved from the concentrated suffering of grieving mothers. He also is said to live within all mankind, waiting for the thin glass wall within them to crack, so that he may take over...
His real name is Z'algatoth.
He takes the eyes, the windows of the soul. Removes the ability to feel... anything but pain. Once the eyes have been removed, the soul is removed. The living husk is testament to cruelty and everlasting doom.
Zalgo's coming is heralded by the fabric of reality itself snarling or screaming "He comes!" and the horrific mutation of web-comic characters and fonts. Gaping, toothy maws, stingers, and masses of tentacles are the norm. Invariably, the eyes turning to black slime and run down their cheeks like tears of oil. Font scrambles and loses coherence.