i would add a fire knight
If You Could Add A New Piece To Chess, What Would It Be?

I would add a Bomb.
It cannot move. It cannot capture. It cannot be captured. The Bomb can do only two things:
1) It can just sit there and do nothing. This is called "Deterrence Mode".
2) It can choose to detonate, destroying the chess-board and wiping out everything on it. This is called "Armageddon Mode".
Detonating your Bomb loses the game automatically and counts the same as Resigning.
It's a form of Rage-Quitting, which might be more fun than just abandoning the game.

Base game is fine, but an interesting variant would be to encode a light/dark square strength to each player at game start by replacing one bishop on each side with a ferz or alfil.

I would add an Archer, to be placed outside the rooks. These pieces can move like rooks and like bishops however, they can jump over one or two pieces to get to their destinations or targets.

what about a dragon that can move like a knight but two more spaces. sry i wrote rook but i meant knight
it can be anything like a cold double knight or a dangerous variant piece.
LIKE ADD ANYTHING YOU WANT? LIKE ANYTHING!