Cellar Door

A piece of old, damp, and rotted wood about 4 inches square; each side of the wood is covered in runes written with Infernal. You can place the square on a flat surface and speak the command word to cause it to grow and expand into a set of double doors large enough to accommodate a Large or smaller creature. The door embeds itself into the ground as it does so. Speaking the command word again causes the door to shrink once more, allowing it to be picked up again. When you open the door, it leads into a small demiplane that resembles a moist, mold-covered cellar, with a packed earthen floor, and rough stone-hewn walls. Attempts to dig through the floor meet with failure, as there is unbreakable stone, similar to that of the walls, only 6 ft. down. The cellar is 30 ft. on a side, and has a faint aura of necromancy magic throughout. If you leave the corpse of a single Large, Medium, or Small humanoid in the cellar for 8 hours, it is automatically transformed into a Zombie or Skeleton (your choice). The cellar can animate only three dead bodies per week. An undead creature animated by the cellar follows your commands for as long as you remain attuned to the cellar door, and can be commanded by using a bonus action on your turn. An undead creature created by the cellar that remains outside of it for longer than 12 hours is no longer under your control, and becomes hostile to all creatures that are not undead. The cellar can hold up to 36 Small or Medium undead, or 18 Large undead. Other dead humanoids placed within the cellar past this number do not animate. If there is a living creature inside the cellar, the door will not shrink down, even when commanded to.