Two bishops cross-mate a queenside king
Two crisscrossing bishops mate a king that has castled queenside. One bishop checks down the long diagonal; the other covers the king's only flight square. A queen sacrifice on c3 (or its mirror) clears the path.
Queen sacrifices on c3. Check. The pawn must take.
Queen does the dirty work. Note the exposure.
3 more clean runs (at any point) to reach Recall.
Black to move. The white king is on c1, walled in by its own pieces. Two black bishops on e7 and f5 are aimed at the queenside.
3 more clean runs (at any point) to reach Recall.