Shellback Carriage

Wondrous item, rare

You can use an action to place this 4-inch wooden turtle carving on the ground and speak its command word. The carving rapidly grows into a Huge wooden carriage that remains until you use an action to touch it and speak the command word that returns it to its carving form, which works only if the carriage is empty.

The carriage is a circular, domed vehicle made of wood in the shape of a turtle, which comes with four walking legs instead of wheels. The interior is 15 feet across and 10 feet high, with windows set around it. Five Medium creatures can fit comfortably inside the carriage, or eight if they squeeze. When activated, the carriage has a small door on the side facing you. The door opens only at your command, which you can speak as a bonus action. It is immune to the knock spell and similar magic, such as that of a chime of opening. The carriage won't move while you're not within it, and its magic prevents it from being tipped over.

You can command the carriage to move using a bonus action. It has a walking speed of 20 feet and a swimming speed of 30 feet. While swimming, its wooden feet transform into oarlike flippers, it is airtight and watertight, and its interior holds enough air for 10 hours of breathing, divided by the number of breathing creatures inside. It has AC 20, 50 hit points, immunity to poison and psychic damage, and resistance to all other damage. If the carriage is reduced to 0 hit points, it's destroyed and reverts to its carving form, shunting everything inside of it to the nearest available space. The carving then shatters and is destroyed. If the carriage reverts to its carving form before losing all its hit points, it regains all of them.

Don't worry, we'll get there when we get there.