While wearing this amulet, you can use an action to name a location that you are familiar with on another plane of existence. Then make a DC 15 Intelligence check. On a successful check, you cast the plane shift spell. On a failure, you and each creature and object within 15 feet of you travel to a random destination. Roll a d100. On a 1–60, you travel to a random location on the plane you named. On a 61–100, you travel to a randomly determined plane of existence.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.