Zarathyn's Silver Tower

You conjure a physical extradimensional Silver Tower, a 20-foot-radius, 60-foot-tall arcane structure of silver stone, impossible geometry, and shifting runes. The tower manifests on solid ground within range and remains anchored at that location for the duration. Its interior is larger than its exterior and serves as your arcane sanctum and summoning reliquary.

The tower is real and tangible and can be entered, occupied, and defended. It has AC 17, 80 hit points, immunity to poison and psychic damage, and resistance to nonmagical damage. If reduced to 0 hit points, the tower collapses into motes of silver light, and the material component used to initially cast the spell is consumed.

As an action, you may store creatures summoned by another spell, up to a total CR equal to your proficiency bonus + your Intelligence modifier, preserving their hit points, conditions, and remaining duration.

As an action, you may remotely retrieve one stored creature, manifesting it in a space you can see within 30 feet, provided the tower still exists and is on the same plane as you. If the retrieved creature requires concentration, you immediately begin concentrating. If concentration cannot be maintained, the creature persists for 1 round before being consumed in a gout of silver flame, destroying it.

You may also remotely recall creatures summoned in this way back into the tower, preserving their hit points, conditions, and remaining duration.

If the tower is destroyed, you lose access to any creatures stored within it. However, when you cast this spell again, any creatures that were stored at the time of its destruction are present within the tower upon its return.

While inside the tower, you may perform a 10-minute ritual to relocate it to any location within 9 miles that you have previously visited.