"The Lurker in Tunnel 13" is a story featured in Swamp Thing Vol 1 #8 which was written by Len Wein, illustrated by Bernie Wrightson, and published by DC Comics in 1974. The plot involves the Swamp Thing facing off against M'nagalah, an Elder God that was terrorizing the town of Perdition.
Synopsis[]
While on the run from the Batman, the Swamp Thing got lost in a snow-swept Appalachian forest where he encountered Ezekiel, an old man who was being attacked by a grizzly bear in a cave. The Swamp Thing managed to fight off and kill the bear but Ezekiel had already been fatally injured, and only lived long enough to warn him not to go into Perdition, a mining town that had been cursed by occult practices after running out of coal. Not wanting to leave him in the cave, the Swamp Thing carried Ezekiel's body in hopes of giving him a proper burial and notifying his family.
After arriving in Perdition, some of the locals mistook the Swamp Thing for the murderer of Ezekiel and attacked him until Ezekiel's son, Jason, pointed out that it could not be the case, as he was clearly clawed to death by a bear. Having also been injured during the attack, Jason brought the Swamp Thing to his house to give him some time to recover; however, this was quickly interrupted when his son, Jody, went missing. Along with the Swamp Thing, Jason and his family went out to search for Jody by following some footprints that led to the forbidden Tunnel 13. As gratitude for his previous acts of generosity, the Swamp Thing decided to enter the tunnel for Jason and risk his own life to retrieve Jody.
The whole thing turned out to be a ruse, however, as the townspeople's true intentions were to trick the Swamp Thing in order to use him as a sacrifice to M'nagalah. Upon entering the tunnel, M'nagalah explained that he was responsible for the creation of all life on Earth and bestowed mankind with the capacity for mindless violence, but was also generous to touch the minds of humanity's greatest scribes (including H. P. Lovecraft, Ambrose Bierce and Edgar Allan Poe). M'nagalah managed to do this from a distant place not of this world and would have stayed there if Abraham, father of Ezekiel and grandfather of Jason, had not spoken the spell that freed him from his distant prison. During his occult practices to restore the town's coal supply, Abraham used the spellbook Visions of a Dead Priest that allowed M'nagalah to slowly manifest in the human world as a growth on Abraham's arm that eventually consumed his entire body, before consuming many others to gain more mass. M'nagalah attempted to devour the Swamp Thing so he could reach his full mass and conquer the entire universe. The Swamp Thing tore off a pillar so he could throw it into M'nagalah, causing the whole tunnel to collapse.
The townspeople began to celebrate, thinking that both of the monsters were dead; however, the Swamp Thing managed to escape from the ruins and Jason begged for mercy. Despite being angered, the Swamp Thing spared him and the threat was seemingly over until it was seen that a piece of M'nagalah was growing on Jason's arm.