Mighty fortress

Mighty fortress was a conjuration spell that summoned a temporary fortress made of stone to rise from the ground.

Effects
The spell created a large fortress that occupied the area of a square on a side. The fortress could be summoned in any visible area within a range of that did not have any previous constructions. It simply rose from the ground, harmlessly lifting any creatures that might have been occupying the area.

The fortress consisted of a square outer wall with four turrets, one on each corner, and a smaller inner keep that occupied a square on a side. The keep had three floors connected by stone stairs and could have any room arrangement and furnishing that the caster desired. The outer wall could have at most four stone doors. Although magical and quite sturdy, the fortress was not indestructible and could be damaged.

The fortress included a compliment of 100 servants similar to the unseen servant spell that followed the commands of anyone designated by the caster. It produced enough food to provide a daily nine-course banquet that could feed up to 100 people.

No items created by the spell could leave the fortress. Any object, piece of furnishing, or uneaten food taken out of the fortress immediately crumbled to dust.

The fortress lasted for seven days, after which it crumbled and harmlessly sank back into the ground, leaving behind any external objects or creatures left inside. If the spell was cast once every seven days for a full year, the fortress became permanent.

Components
The spell required verbal, somatic, and material components. The material required was a diamond worth at least 500 gp, which was consumed by the spell.