Wandenreich

The 'Invisible Empire' of Yhwach's Quincy, hidden for a thousand years in the shadows of the Seireitei. It declares war on the Soul Society with five days' notice.

It prepares for war by invading Hueco Mundo and enlisting the Arrancar, then strikes the Seireitei with the Sternritter and the Bankai-stealing medallions. In the second invasion it replaces the Seireitei with Silbern, then follows Yhwach up to the Reiōkyū, which becomes Wahrwelt.