These opalite Swarovski crystals represent the poison necklace worn by Sansa Stark during the wedding of Joffrey to Margaery.
Unbeknownst to Sansa, she had smuggled in the fatal "Strangler" poison supplied by the Queen of Thorns (Olenna Redwyne Tyrell).
During the chaos of the murder, Sansa had to flee King's Landing with the help of Littlefinger who revealed to Sansa that she had been involved in the killing through this necklace.

The necklace hangs at 20 inches but can be made shorter upon request.

*Game of Thrones, A Song of Ice and Fire and House Stark are copyright George RR Martin. I a