Meisterwerke

Retract -1. .. Rg6-f6 -2. Na3-b1 Rf6-g6 -3. Nc4-a3 Rg6-f6 -4. Ne3-c4 Rf6-g6 -5. Nd5-e3 Rg6-f6 -6. Nf6-d5 b7-b6 -7. Nh5-f6 Rh6-g6 -8. f6-f7 Rh8-h6 -9. e5xRf6 h6xNg5 and the position unlocks. So black moved last. #1 with 1. Be1#.

Solution by Philippe Schnebelen