At this point, I can envision whites pawns marching down leading to a pretty dangerous attack. Better put something in their way.
18... Qd8h4
!? This stops castling, but already I could see the danger in the queen being trapped.
19. Ke1d2 Ra8d8 20. Ra1g1 f6
?! OK, the knight is trapped, but two pawns for a knight and a fairly open route to the King. I am not sure this is right.
21. Ne5xg6 hxg6 22. Bc2xg6 Re8f8 23. Bg6h5
? This seems to give up the momentum. Pg5 seems better to me, but I have not looked at all the possibilities.
23... e5
! Now, the tide turns
24. Bf4g3 Qh4g5 25. f4
? The trap was missed. P-H4 was better. The threat here for black was if PxP, then BxPf4 does actually trap the queen. However there is a way out.
25... Nd6e4
! The trap is sprung. Wherever the K moves. Ne4xBg3. Now Pf4xQ is matched by Nf3XQ and after PxP and KxN black is a knight up with compensation. or Rf1xNf3, Pd5xPf4, Pe3xPF4, Qg5xPf4 and again black is a bishop up with a good position. White resigns.