The Returnal: Ascension update added co-op and a new game mode: the Tower of Sisyphus. It's an endless mode where players fight their way through the floors of a tower that dominates the landscape. This guide explains how to find the tower so that you can start your first ascent. Where is the Tower of Sisyphus? Screenshot by Gamepur You can find the Tower of Sisyphus close to Helios, Selene's ship, and the base you return to after every death. Instead of heading left to start the cycle afresh, run forwards towards the new ledge and door. You'll need to have unlocked the Grapnel to get up to this door, but once you have it, you can go through and access the Tower of Sisyphus from your spawn point. You don't need to do anything else special to access this endless game mode. Beyond the door, you'll find the tower and the portal to interact with it. When you're ready, head into the portal, and you'll be teleported over to the tower to begin your nightmarish journey through its floors to a brand new boss. This game mode can only be played solo, meaning you can't bring a friend or random other players with you to try to make each floor easier to battle your way through.