Swamp Thing by Rick Veitch. Book 3. Time Upon a Once

"Thrust backwards in time, Swamp Thing must make sense of a universe drawing him towards its very inception. With the birth of the Sprout approaching, Abby desperately searches for answers and her missing husband while a monstrous entity from the past watches and waits. John Constantine will do whatever it takes to bring the Swamp Thing home before Hell, the Green, or worse comes to get them!"-- Provided by publisher.