Heartbinder

Heartbinders are collectable items introduced in Kingdom Hearts III that allow Sora to summon allies to assist in battle.

Kingdom Hearts III
After their adventures in Olympus, Sora, Donald, and Goofy return to The Mysterious Tower, where Master Yen Sid tells Sora to continue on his search for the power of waking with the end goal of saving Aqua. Before they depart, Yen Sid gives Sora a departing gift: a Heartbinder. Master Yen Sid explains that Sora had a gift for connecting with others and the charm will make it stronger. Sora clutches the Heartbinder tight before he and his friends take their leave.