Wow! What kind of variant?
Well my idea for a long time was to try to steamline and sort-of-rationalize chess by removing everything that felt like artificial ad hoc rules and solve some of the known problems at high level (opening tend to be predictable going-through-the-motions affairs, and games disproportionally end in draws).
So the end result looks like this:
The two side boards are not necessary, they're for convenience, the game can be played on a regular chess board.
The following differences with chess are found:
-Players start with all the non pawn pieces offboard. The game start with a phase of deployment where players deploy alternatively: their kings; their rooks and princes (see below); their bishops and knights. The pieces are placed wherever the players want behind their row of pawns. The only restrictions are that 1) the two kings must be on different files; 2) a player's rooks cannot be on the same file as each other or as the enemy king; 3) the two bishops of a single player must be on differently colored squares. Once the deployment phase is complete, the game procedes as normal, with the player who was first to deploy being second to play.
-The pieces are the same in chess, with the following exceptions: the queen is replaced by two princes, who can either move 1 square in any direction, or jump over one square in any orthogonal or diagonal direction (so a prince in the center of the board can reach 16 squares). The pawns have the following movement: they can move
and capture one square directly forward or backward, or diagonally forward (thus having four possibilities of movement).
-The dropping rule of Shogi (Japanese chess) is used: instead of moving a piece, a player can drop a piece they have captured from their opponent on any empty space of the board, under their control. (The game is meant to be played with reversible tokens à la Otello/Reversi to do this easily).
-There are no conditional special rules: no promotion, no castling, no initial double movement of pawns.
A few playtests have shown the game to be rather more fast paced and violent than chess, while remaining tactically deep.