In Dark Daneil's universe, Benjamin Malkator was successful in becoming a Fear and ended up giving in to his inner darkness just like The Mother of Snakes predicted. Malkator eventually lost his humanity and went on a killing spree during which everyone close to Dark Daniel was killed. Dark Daniel was ultimately forced to kill Malkator despite their previous friendship and spiraled into depression. The mainstream Daniel received a vision of this event years later while he travelled through the Path of Chaos to gain one half of a key from The Sentinel.
After being pulled into the Daniel-Verse, he decided to try to murder and replace Daniel, having lost everything that mattered to him in his own universe. After fully mutating, his motivations changed from replacing Daniel to destroying him. Dark Daniel was killed when Daniel impaled him and the Archangel, on the end of his own sword.
He is identical to Daniel, and wears a plaid jacket which is damaged in several places. However, after being consumed by rage, his body mutated even more than ParaDan's, causing him to develop pale skin, black and white hair, and black markings all over his body.
Dark Daniel is much more sinister than Daniel is.
Dark Daniel posses all of Daniel's powers, but is much stronger.
He was able to suppress the mutations normally caused from the use of the Devil Killer abilties for a long time. Alongside this, he had acquired the abilities of every Fear in his universe. Unlike Daniel and ParaDan, he is able to use multiple powers at once.
ParaDan stated that Dark Daniel is stronger than both him and Daniel.
The only weapon Dark Daniel has been seen with a katana. He is able to use the Empty City's power to alter the size of his sword, and it is currently 12 feet long.