I like the concept of integrating chess into a roguelike game. I finished the game once after maybe 5 tries, understanding attack patterns of enemies.
The strategy for the virus looking enemy (Honestly don't know how else to describe) is to kill them last. (So there'll be less enemies on the board.) Wait till it touches the sides of the board, reducing the spawn upon death by 2. Better if it's in the corner, where only 1 would spawn on death. Either escape to a safe tile (if the one you're on after attacking the virus is attacked) or just end the turn. Do not attack the spawns as they leave a 3x3 attack pattern from where they die. Only engage one of them for the start of each turn, while escaping to a safe tile the next turn with bishop/knight/queen/rook. If unable to escape on second turn, don't attack the first turn and move to a safe tile.
Attack the ninja enemy first. It doesn't leave a 3x3 attack pattern unlike the virus spawns and it usually stays away from you while attacking tiles from far.
What I hope could be improved are :
1. A tutorial. I almost quit after trying to drag the card onto the board. Wasn't really intuitive for me. I knew how chess pieces move but would be great for players new to chess to have a tutorial on how each piece moves too. (The direction "arrows" after clicking a card may not be intuitive for new players.)
2. 4 pawns in one hand. When you get stuck on the top rank and the tile is under attack, isn't really fair. Increasing the card pool may decrease the chances, but maybe some sort of guarantee would be good. (Maybe every 2 card gain reduces the maximum number of the same pieces you can get in a hand from 4 by 1.)
3. Background music.