2024 rules reference for Robe of Stars.
Wondrous Item
This black or dark-blue robe is embroidered with small white or silver stars. You gain a +1 bonus to saving throws while you wear it.
Six stars, located on the robe's upper-front portion, are particularly large. While wearing this robe, you can take a Magic action to remove one of the stars and expend it to cast the level 5 version of Magic Missile. Daily at dusk, 1d6 removed stars reappear on the robe.
While you wear the robe, you can take a Magic action to enter the Astral Plane along with everything you are wearing and carrying. You remain there until you take a Magic action to return to the plane you were on. You reappear in the last space you occupied or, if that space is occupied, the nearest unoccupied space.