The Darkstars #21

Former Green Lantern John Stewart is approached by the Darkstars' masters, the Controllers, for a mysterious mission. And former New Titan Donna Troy gets an invitation she can't resist. Plus, the Darkstars go to the origin world of the Annihilator virus to find a cure for Flint. But in order to get it, they have to protect its creators from a group of otherworldly heroes seeking vengeance.