The Key of Lorelei is a powerful weapon in Tales of the Abyss created by Lorelei, the aggregate sentience of the Seventh Fonon, that allows the user to summon the sentience when used alongside the power of the Grand Fonic Hymn. It also allows the user to use Lorelei's power at will. The complete Key is actually two parts: a sword, also called the "Key of Lorelei", which concentrates fonons, and the Jewel of Lorelei, which disperses them.