Release is a job ability command given by a Summoner to their Avatar in Final Fantasy XI. After an avatar or elemental is summoned, it will stay and await instructions by the Summoner. During this time the summoned creature will slowly drain MP from the summoner. The amount of this drain is determined by the summoner's level, which avatar it is, and the summoner's equipment. While the avatar is out, the summoner will also be unable to rest to recover MP.
When a summoner uses Release, they instruct the summoned creature or elemental to leave. It is earned at level 1 and can be recast every 10 seconds. Any enemies that only have hate on the avatar (like others of its species that linked on the avatar when the avatar was attacking) will deaggro when Release is used if no party members took action against those monsters.