This just in from DC Comics' blog The Source:
With the reveal of Swamp Thing as the Dark Avatar, "BRIGHTEST DAY" gears up full-force to its epic finale. A plant/human hybrid, Swamp Thing first appeared in 1971 in the early-20th-century-based "HOUSE OF SECRETS #92," written by Len Wein, fan-favorite for his super hero adventures, and legendary horror artist Berni Wrightson. A year later, he returned as the star of his own series set in the contemporary DC Universe.
In this series, it was revealed that Swamp Thing was once completely human, in the form of scientist Alec Holland. When a bomb went off in his lab, Holland retreated to a nearby swamp and materialized as the plant elemental, Swamp Thing.
Throughout the years, there have been many different takes on Swamp Thing’s origins. In Alan Moore’s historic run, it is revealed that he was not in fact a reincarnation of Alec Holland, but rather a member of an ancient group of plants called the Parliament of Trees, and had only absorbed all of Holland’s memories and personality. It is this same Parliament of Trees that The Elementals must now protect in "BRIGHTEST DAY."
The star of four of his own series (1972, 1982, 2001, and 2004), Swamp Thing has had his stories intertwine with other supernatural characters in the DC Universe, including Phantom Stranger, Demon, Deadman, and on occasion, the Justice League of America. He has also repeatedly crossed paths with Batman, has lived alongside Pamela Isley (a.k.a Poison Ivy), and has taken on Lex Luthor (in issues 52-53 of "SWAMP THING VOL. 2") in the mid-80’s – around the same time he visited the abandoned Cambridge mansion in Crisis on Infinite Earths. His “American Gothic” storyline was just re-published in the hardcover, "Saga of the Swamp Thing: Volume 4."
With the ability to regenerate by turning any matter into his own body mass, Swamp Thing is a creature of monumental power and is quintessential to the DC Universe. After having been absent for so many years, what does his return signify?