what is bankai in bleach

In the anime and manga series Bleach, Bankai is the second and final upgrade for a Zanpakutō, which is a sword-like weapon used by the Shinigami, or Soul Reapers. To achieve Bankai, a Shinigami must summon and subjugate their Zanpakutō spirit, which is the manifestation of the spirit itself, usually creating a massive creature or effect to aid the user. Unlike shikai, there is no command phrase to activate Bankai, though a Shinigami will typically say "Bankai" beforehand. The Zanpakutō also changes into a more evolved form, and the user gains new abilities, which could be an elemental or illusionary power, poison ability, melee attack, or a Kido ability. The power that comes with Bankai either augments the original abilities of a Zanpakutōs shikai or follows the general theme. The Bankai is that spirit’s strongest power, and making the Zanpakutō spirit appear and submit is only required for the training and to achieve Bankai.