-Generator variant, called "Matrix" ?
-Peces on first rank never move but generate new pieces. Pawn don't generate.
-A generator captured and replaced by a similar piece does not generate.
-King does not generate. No castling. En passant possible?
-Goal is still checkmate.
+Monster, Horde, Colorbound
+https://www.chessvariants.com/d.betza/chessvar/dan/colclob.html
+https://lichess.org/analysis/horde#0
+https://greenchess.net/rules.php?v=monster
+https://en.wikipedia.org/wiki/Monster_chess
+https://en.wikipedia.org/wiki/Grotesque_(chess) (fun)
+
+Maxima, Interweave, Roccoco
+https://www.chessvariants.com/other.dir/rococo.html
+https://www.chessvariants.com/dpieces.dir/maxima/maxima.html
+https://www.chessvariants.com/other.dir/interweave.html