The Hall of Fallen Foes is a new feature in the Switch 2 remake of Zelda: Ocarina of Time. It records enemies encountered during the adventure and lets players take on defeated bosses again in a boss-rush-style challenge.
To unlock it, first become Adult Link and complete the Forest Temple. You can then return to Child Link at the Temple of Time. As Child Link, approach Kakariko Village from Hyrule Field. Kaepora Gaebora will stop you before the village and explain how to reach the Hall.
The Hall can be entered by sleeping in a bed that glows green. One nearby option is the Grand Lodge in southern Kakariko Village. Choose to sleep and dream at a glowing bed to wake up inside the Hall, where you can review defeated enemies and find bosses around the outer edges for rematches.
To leave, speak to Kaepora Gaebora. Items and resources used during the Hall’s challenges are replenished when you return to the main adventure.
Sources: Nintendo Life.