Coruskian Stone

Set in a golden necklace, this green stone was originally enchanted by a Nyrondese wizard who sought to control the griffons of the Coruskian Mountains. While you wear this magic item, you can use a Magic Action to magically conjure a griffon within 1 mile of you. The griffon appears in an unoccupied space within 60 feet of you, has the Charmed condition and is Friendly to you and your allies. You can ride the griffon and you are proficient in it. The griffon disappears after 1 hour or earlier if you dismiss it as a Bonus Action. Once you use this property, you can't use it again until you finish a Long Rest. If there aren't griffons within 1 mile of you, nothing happens, but you haven't used this property. The DM has the statistics for the griffon.