As a Magic action, you can place this 1-inch adamantine statuette on the ground and, using a command word, cause it to grow rapidly into a square adamantine tower. Repeating the command word causes the tower to revert to statuette form, which works only if the tower is empty. Each creature in the area where the tower appears is pushed to an unoccupied space outside but next to the tower. Objects in the area that aren’t being worn or carried are also pushed clear of the tower.
The tower is 20 feet on a side and 30 feet high, with arrow slits on all sides and a battlement atop it. Its interior is divided into two floors, with a ladder, staircase, or ramp (your choice) connecting them. This ladder, staircase, or ramp ends at a trapdoor leading to the roof. When created, the tower has a single door at ground level on the side facing you. The door opens only at your command, which you can issue as a Bonus Action. It is immune to the Knock spell and similar magic.
Magic prevents the tower from being tipped over. The roof, the door, and the walls each have AC 20; HP 100; Immunity to Bludgeoning, Piercing, and Slashing damage except that which is dealt by siege equipment; and Resistance to all other damage. Shrinking the tower back down to statuette form doesn’t repair damage to the tower. Only a Wish spell can repair the tower (this use of the spell counts as replicating a spell of level 8 or lower). Each casting of Wish causes the tower to regain all its Hit Points.
Notes: Immunity: Bludgeoning, Immunity: Piercing, Immunity: Slashing, Resistance: All
No more palace nuke! Lol cool
Takes attunement, is a big pointless house. A determined group of peasants with torches could eventually destroy it.
Seems neat
Torches aren’t siege weapons as it’s immune to all damage except dealt by siege weapons.
Bug on the sheet. When equipped it grants its invulnerability and resistance to the wielder. xD
It's only resistant to fire damage, so torches could eventually destroy the Fortress.
That said, by the time a party has something like this, a group of peasants with torches could be dealt with using a single well-placed Fireball. :)
However, a Warlock with Eldritch Blast and Eldritch Spear could just sit hundreds of feet away and blast the Fortress with Force damage until it, I assume, crumbles... the item description doesn't indicate what happens if a single side loses all of its hitpoints, or if all sides lose them all, etc.
It seems like this item's description and abilities needed to be reworked for 5e/5e24.
RE: @lexgamer
I just ran into this in my game. We were all very confused while adding this to my sheet