Thank you for sharing such amazing game! Idea, game concept and development is just very clever! I didn't play such new experience with chess since Navia Dratp.
Surely you already know but there is an issue with basic pawn cards retaining higher cost (e.g.: 2 diamonds; means card design/effect/text reverts to basic card expect the cost) for next round when they were promoted in a previous round. Also at end of the round you cannot banish a card promoted during round.