Sky Tyrant was a past life of Hawkman who was a villian on the parallel universe of earth 3. He was defeated and killed by the Shadow Sheriff and his allies, not before Sky Tyrant promised to find a way to return and nver die again.
The identity of the Sky Tyrant take possession of the body of Hawkman in the present when the Batman who laughs infected him with matter of the dark multiverse, becoming one of the Secret Six infected. Now possessing a body again, Sky Tyrant helped the Batman who laughs before go in his personal journey after the search of immortality. For that he is using the Black Journal, where Hawkman put terrible, forbidden secrets.
However the mind of Carter Hall still resist the Sky Tyrant possession and haunts him in his search, as a ghost. Also behing his trail, Hawkwoman is hunting him.