I have seen some posts on ideas for variant combinations.
What about a variant that combines horde chess, crazyhouse, and three checks, along with an additional rule that if the pieces can capture 4 pawns along the same file, rank, or diagonal, the pieces win?
What about a variant that combines horde chess, crazyhouse, and three checks, along with an additional rule that if the pieces can capture 4 pawns along the same file, rank, or diagonal, the pieces win?