what's that?
Ok, here are the rules real quick:
New pieces: Elephant (Knight + Rook), and Hawk (Knight + Bishop).
Every time you move a piece from your back rank for the first time, you have the option of placing a Hawk or Elephant. Each player gets 1 Hawk and 1 Elephant to place each game. Pawns can promote to Hawk or Elephant.
I think Seirawan Chess would be a good variant to add.