Red Question Mark - Secret room on map Inaccessible - TBOI Repentance

Question

There is no way I can find to get to this room I circled and have never seen it before. I am on the corpse floor 1.

Answer 1

These red secret rooms are called Ultra Secret Rooms. They can only be accessed by creating a new room adjacent to it or by teleporting to it using the reversed card "XVIII - The Moon?". You can create new rooms by using the item Red Key, the trinket Crystal Key, or the consumables Cracked Key or Soul of Cain.