Navigation Orb

From Storm King's Thunder, page 235.

Description
Wondrous item, very rare (requires attunement).

A navigation orb is a hollow, 7-foot-diameter sphere of thin, polished mithral with a large skye (cloud) rune embossed on its outer surface. The orb levitates 10 feet above the ground and is keyed to a particular cloud castle, allowing you to control that castle's altitude and movement while the orb is inside the castle. If the orb is destroyed or removed from its castle, the castle's altitude and location remain fixed until the orb is returned or replaced.

As an action, you can cause one of the following effects to occur if you are touching the orb:
 * The castle moves at a speed of 1 mph in a straight line, in a direction of your choice, until the castle stops or is made to stop, or until another action is used to change its direction. If this movement brings the castle into contact with the ground, the castle lands gently.
 * The castle, if it is moving, comes to a gradual stop.
 * The castle makes a slow, 90-degree turn clockwise or counterclockwise (turning a northerly view into a westerly view, for example). The castle can turn while it is moving in a straight line.
 * Any creature touching the orb knows the altitude of the base of the castle above the ground or water below it.