Katar Hol and Shiera Thal must face Byth of Thanagar in the Downside!
Thanagar—a world ruined in a war with its sister planet Rann—
One Thousand Years Ago...!
Thanagar and its twin orbit the Alpha Centauri Star System, our sun’s closest stellar neighbor—a system of three stars...  the two ancient Earth-like planets orbit two of the stars in such a way that while both worlds have two suns in their skies, the planets themselves only get very close to each other once in a millennium...  The third star in the Alpha Centauri System, a white dwarf, is even further away from the two stars as Jupiter is from our sun...
 

Winged Hawk-warriors from the planet Thanagar awake to the knowledge of their reincarnated selves in the bodies of archaeologist Professor Carter Hall and his graduate assistant Shiera Thrash—giving the two of them the power of Hawkman and Hawkwoman.  They discover that the Thanagarians had actually reached Earth, where they died.

In the wreckage of the craft, they discovered the armor of the Thanagarian police, including the helmet, the wings and the harness of Nth Metal.