Short range leapers can be quite powerful. I suspect that your Mammoth is worth as much as two Bishops, even on a 10x10 board.
Some of us remember an earlier game called Mammoth Chess, which has since disappeared from sight. Nothing stopping you from using the name for your new variant.
Some of us remember an earlier game called Mammoth Chess, which has since disappeared from sight. Nothing stopping you from using the name for your new variant.