Source: Spelljammer: Adventures in Space - Astral Adventurer's Guide

Wondrous item, Rare (Requires Attunement by a Spellcaster)

The function of this ornate chair is to propel and maneuver a ship on which it has been installed through space and air. It can also propel and maneuver a ship on water or underwater, provided the ship is built for such travel. The ship in question must weigh 1 ton or more.

The sensation of being attuned to a spelljamming helm is akin to the pins-and-needles effect one experiences after one's arm or leg falls asleep, but not painful.

While attuned to a spelljamming helm and sitting in it, you gain the following abilities for as long as you maintain concentration (as if concentrating on a spell):

• You can use the spelljamming helm to move the ship through space, air, or water up to the ship's speed. If the ship is in space and no other objects weighing 1 ton or more are within 1 mile of it, you can use the spelljamming helm to move the vessel fast enough to travel 100 million miles in 24 hours.

• You can steer the vessel, albeit in a somewhat clumsy fashion, in much the way a rudder or oars can be used to maneuver a seafaring ship.

• At any time, you can see and hear what's happening on and around the vessel as though you were standing in a location of your choice aboard it.

Transfer Attunement. You can use an action to touch a willing spellcaster. That creature attunes to the spelljamming helm immediately, and your attunement to it ends.