Known as the Avatar of the Green, Swamp Thing is an the embodiment of the cosmic energies that gives life to all plant life in the known universe (dubbed "The Green") and is considered the champion of the Parliament of Trees, the collective guiding and collective consciousness of all plant life.

The first Swamp Thing was '''Alexander Olsen''', a scientist who was killed by his assistant vying for the affections of his wife. Returning as a swamp creature after his body is dumped, he takes revenge