User blog comment:B214/Question and Answers 6/@comment-24409634-20160927141510/@comment-1359322-20160927142117

You can't change your Evil Piece, it's a one time deal once you made him/her into a Bishop, that person can't change his piece anymore.

"“There’s a saying like this in the world of chess. Queens have a value of 9 Pawns. Rooks have a value of 5 Pawns. Knights and Bishops have a value of 3 Pawns each. Like this, there are standard values that also apply to the Evil Pieces. A similar phenomenon happens to those reincarnated. If there are those who can only be reincarnated with 2 Knight pieces, then there are also those who need 2 Rook pieces to be reincarnated. There’s also the compatibility with the pieces as well. You can’t use 2 separate Pieces to give them different roles, so it’s important to think how to use the pieces. Once you use it, Devils won’t be given a new [Evil Pieces].”"

- Volume 1