Spelljammer-Adventures In Realm Space
Crown of The Stars
Cost-A King’s Ransom, At Least
This magical item distills the abilities of a minor helm into a portable item that can be worn, allowing the helmsman to move normally in addition to commanding his ship. Despite its name, a Crown of the Stars is not necessarily a crown; it may be a torq, or a necklace, or a girdle, or any other item which can be worn. It cannot be a ring, however. The only known Crowns of the Stars are significantly larger than rings, and all contain at least some silver.
If the crown is used to power a ship for one week or more, it becomes bonded to that ship. It cannot be used to power a different ship unless it has been away from its bonded ship for at least one week, thereby severing the bond.
The Crown of the Stars is effective up to one mile away from the ship it is bonded to, so a helmsman can operate the vessel even if he is not on board.
A Crown of the Stars will not affect a ship with an active helm (or equivalent) on board. It can provide spelljamming ability to ships that would otherwise lack it (such as a viking longship). Often a crown is discovered on the ground where they befuddle the local sages, who do not know of the worlds spinning above their heads.