13 BLADEs. is a special commemorative databook in released in 2015 to celebrate the 13th anniversary of Bleach.
The book contains an interview with Tite Kubo, the results of several popularity polls that had been run in Weekly Shonen Jump as well as information on the Bleach: Brave Souls game. It also contains a short novel called Beginning of the Revive of Tomorrow and a special manga chapter called 520.5. WALK UNDER TWO LETTERS that was later collected in volume 70.
Beginning of the Revive of Tomorrow
Beginning of the Revive of Tomorrow is a short story by Ryōgo Narita. The story takes place during the second invasion of Seireitei by the Wandenreich. The Sternritter Shaz Domino attacks the Central 46 chambers, intending to find information about the Hōgyoku so that he can transcend his limits and become a Hollowfied Quincy. He encounters and is defeated by a revived Izuru Kira.