This crown belongs to Tarquin, the High Lord of the Summer Court.
History[]
A Court of Mist and Fury[]
When Rhysand, Feyre Archeron and Amren went to the Summer Court under the pretext of meeting with the High Lord, Tarquin, when They were actually looking for half of the Book of Breathings that he had in his possession, they were received by the High Lord and a delegation comprised of his cousins Cresseida and Varian, the Princes of Adriata and three advisers.
On the very night of their arrival, Tarquin invited them to dine in the Pleasure Barge to celebrate their visit where, accompanied by around one hundred High Court Fae, they sailed the shores of Adriata while dining and drinking. At dinner Tarquin was wearing a crown that looked like the crest of a wave adorned with sapphires and white gold. After he noticed that Feyre was looking at it he joked that with the amount of skilled jewelers in his court one would think they could make a more comfortable crown since that one hurt.