A step by step guide getting the Avenged achievement.
The Black Bishop is a secret boss you can fight on floor 12, after killing the White King. He’s quite strong so make sure you have a good build going.
This guide will show you how to summon him, and get the Avenged achievement if you manage to defeat him.
You will need two White modifiers in order to get the encounter.
The Red Book
It can get quite tricky fighting against multiple bishops so try not to get too many of them or giving them other modifiers, although I recognized if you give them buffs these two are more likely to appear but that maybe a coincidence.
The White King fight is as normal as it is with one exception: 1 Bishop must survive in the end.
My advice is to keep distance from the king while you clear other pieces. The Moat is a good buff which gives you more time. A sniper build also works.
If you are successful the bishop transforms.
Instead of trying to chase you the Black Bishop summons pieces to fight for him. It may seem better to finish him fast but be aware that things can get out of hand quickly so keep some shells for the minions.
If you succeed you will get the achievement and a secret ending.
also if you have 1 bullet left in the chamber after killing him you will get a different ending!