!? The threat that has been there for quite some time. Whether this is actually a good move or not is another matter.. probably not. But an interesting one.
11... Qe7xf7
Had to, Kxf7 would've meant Nxe5 double check, and the bishop at g4 falls.
12. h3 Bg4xf3
Necessary.
13. Rf1xf3 Qf7e7 14. c3
Builds the center. Offers a trap - exd4 cxd4 Qxe4 Re3, and the black queen falls.
14... O-O-O 15. Qd1a4
Shifts the attack to the queen side of the board.
15... Kc8b8 16. Bc1e3 c5
the pawns are the castle walls of the black king. Moving them should be done as last resort, especially as the bishop at f8 and the rook at h8 remain idle. exd4 could've been considered though as the black pawn there is solitary.
17. d5
Refuses to give up the center, making it the white king's best defense. Also opens the bishop's line.
17... Qe7d6
Better to bring the rest of the guns to bear. e.g. g5, Bg7, Rhf8 to contest the open f-file and to protect the e-pawn better. This one yields the f7 square.
18. b4
tries to open the line of pawns defending the king
18... Rd8c8 19. Rf3f7 Rc8c7 20. Ra1b1
All of white's forces point at the black king. Black has a material advantage, but two major pieces remain idle.