There are two endings players can unlock in Dredge, either the standard "bad" ending or a secret "good" conclusion that gives a bit more context to the events of the story. While one ending is found as players normally explore the story, the secret ending comes from tracking down an elusive NPC. Either option is determined once players collect all five Relics and sail toward the marked G-8 spot on the map to end the game.
Careful! From this point on, expect heavy spoilers for both story endings for Dredge. The cut-off point that determines what ending players get is right before they embark on the game's final voyage to G-8. Players should save right before this point, before doing anything with the collected Relics, to reload the game to experience both endings. This is also a great way to find whatever collectibles are on the map or finish any side quests involving the Figures for some last-minute rewards.
How To Unlock The Bad Ending
The bad ending is far easier to unlock since players usually encounter this by progressing normally through the story. The one way to guarantee this conclusion involves handing over all the Relics to the Collector on Blackstone Isle. Making the last journey to G-8 shows a pillar of red light to help guide players to their final destination.
Going to the white question mark and selecting a prompt to interact with it plays the final cutscene, where an ancient god is summoned to start the apocalypse. However, the appearance of this entity abruptly ends the game without any direct explanation about what just happened.
How To Unlock The Good Ending
Going to a ruin located in the Devil's Spine, or section P-10 of the map takes players to an unmarked island where they must speak to the Old Mayor NPC after collecting all 5 Relics. His story reveals that he had gone mad from a sea monster attack out at sea and leads players toward the Lighthouse Keeper at the starting town of Greater Marrow. She tells players of the Crimson Book of the Deep, but only when they ask about the artifact.
The key to getting this ending is discovering this hidden truth and concealing the Relics found from the Collector. Asking the Collector about the Book lets players take the Book from him, which opens up a new mission to return to the Lighthouse Keeper. Once players tell her that they are ready, they need to sail to G-8 and throw back the Book into the ocean, unlocking the secret ending.
The game's biggest secret is that the unnamed main character is the Collector, who lost his memories. The good ending alludes to this, revealing crucial details about the discovery of the Crimson Book by the Fisherman and his wife. Unfortunately, while some story background is revealed through every Message in a Bottle found in Dredge regarding the wife, all players need to know is that she was killed by the dark powers of the book, which the Old Mayor and Lighthouse Keeper both witnessed.
Unfortunately, the final ending players can unlock in Dredge sees the Fisherman get eaten by a Leviathan fish that attacks the player's boat, but this does not summon an ancient sea god to destroy the world, so this might be a slightly better outcome.