Returnal has a few different acts and rolls credits after Act 2. But there is a trophy called “White Shadow” for completing Act 3, which players don’t get for running through the game again. Here’s how to unlock Act 3 in Returnal and get the secret ending.
How to get to Returnal Act 3 for the true ending
To get to Returnal’s final act and get the true ending, players first have to find every piece of the Sunface Fragment in the game. There are six total pieces and one is found in each of the game’s six biomes. Selene should make a comment after picking one up. The game keeps track of this stat in the Databank portion of the pause menu under “Equipment.”
Once all six pieces have been found, players have to go back to the house in Echoing Ruins (which is in every version of the level no matter what). It’s probably possible to go the house in the Overgrown Ruins, but that would just add more work, given the next step.
The door should now be unlocked and let players right in. She will make a note of this being the last time she will return home.
Once players have visited the house for the final time and unlocked the “Sins of the Mother” trophy, they then have to go beat the final boss yet again. This can be done on the same loop.
After beating the underwater monstrosity, proceed down the last pit like normal and go interact with the car in the water. This will trigger the final cutscene. The credits will play and the trophy will unlock.
The Sunface Fragment locations in Returnal are tough to exactly nail down since the game’s levels are procedurally compiled, meaning that it’s impossible to lay out an exact map leading to every piece. However, all of the Sunface Fragments can be retrieved using gear from the last two biomes.
By returning to the first four biomes with the later gear, players can easily pick out where these items are.
After getting the Delphic Visor, look up and find orbs to shoot to reveal new platforms in the other biomes.
Be thorough and look at every diamond item icon on the map. Many of them, including the one in Fractured Wastes, come after getting the Delphic Visor.
The fragment in the Echoing Ruins does require the optional suit upgrade called the Promethean Insulators.
That upgrade should be in the central hub side room (the dark blue triangle) of Fractured Wastes.