Walk-In Closet

To cast a Room spell, choose a half (or "door") to cast. There's no way to cast both halves of a Room card. When the Room spell resolves, the corresponding door becomes unlocked as the Room enters.

Some doors have abilities that trigger whenever you unlock that door and require one or more targets. You can unlock that door even if there would be insufficient legal targets for that triggered ability. The triggered ability won't go on the stack.

Forgotten Cellar's ability won't stop tokens from going to your graveyard as normal (and ceasing to exist shortly thereafter, also as normal).