The Chthonic Island is a fictional island in the Marvel universe which first appeared in 2016 in the 2nd Carnage comic book series in issue #10.
The Chthonic Island is located in one of the world's busiest sea lanes, yet it's not on any map, doesn't show up on radar, nor an any satellite photo. It's an island located in the Sea of Timor, a sea between Australia and the former Indonesian island of Timor. An island which is populated by the Broodlings of Chthon and on it is the Temple of Chthon. For centuries, human sailors have been drawn to the island. Where they were raped to propagate the species and then sacrificed to Chthon, one of the Old Ones.
Recently the psychopathic supervillain Carnage visited the island. Upon his arrival on the island, he was ambushed by the Broodlings who herded him to the temple. Where rather than permit himself to be sacrificed, he slaughtered many Broodlings. The survivors fled and summoned Chthon who devoured many of the survivors. Chthon then attempted to bring others of his kind back to Earth, to rule it beside him. He was stopped by a symbiote-empowered Jubulile whose power was boosted by Victoria Montesi (of the Children of the Midnight Sun). Who read the Darkhold, using a spell to increase her ability to absorb psychic power, both of the light, and dark.