After
[FEN ""]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6. Bg5 e6 7. f4 Qb6 8. Qd2 Qxb2 9. Rb1 Qa3 10. e5 dxe5 11. fxe5
what are black's main strategic goals? As this is supposed to be extremely sharp and complicated, what are the pitfalls to avoid?
[FEN "rnb1kb1r/1p3ppp/p3pn2/4P1B1/3N4/q1N5/P1PQ2PP/1R2KB1R b Kkq - 0 11"]
It would be strange it it were possible to give a short list of pitfalls for one of the most complicated variations in chess. I'll try to give some hints, I don't play it from either side but I'm an opening nut.
First, you've chosen to include 10.e5 dxe5 11.fxe5 but the interesting position is the one after 9...Qa3, where black has chosen to accept the so-called Poisoned Pawn. The other really big main line is 10.f5, and the strategy is similar (white tries to checkmate black).
Also first, the current big fashion for black is to play 7...h6 8.Bh4 before playing 8...Qb6. So if you're looking for recent games, look for games with that included as well.
In the position after 9...Qa3, white has a huge lead of development. Black has an extra pawn and the better pawn structure. Fundamental Chess Openings says "It is in fact very attractive for White to offer this pawn, and it is equally attractive for Black to take it. An ideal setting for a ferocious fight!"
White's strategy is to go all-out to checkmate black's king, as he's burned his bridges already. Black's strategy is to survive the onslaught and somehow return to a normal position (develop his pieces, return his queen to a more normal square) and if he manages that, he'll often be winning. Theoretically, chess is of course a draw, which means here that many of the long, long calculated out lines end up with white having just enough attack to give perpetual check, but not checkmate.
An example from FCO:
[FEN ""]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 e6 7.f4 Qb6 8.Qd2 Qxb2
9.Rb1 Qa3 10.f5 Nc6 11.fxe6 fxe6 12.Nxc6 bxc6 { Now comes a second pawn sacrifice
to speed things up } 13.e5 dxe5 14.Bxf6 gxf6 15.Ne4 { This is the starting point of
variations, based on themes like } 15... Be7 16.Be2 h5 17.Rb3 Qa4 18.Nxf6!? Bxf6
19.c4
"It seems incredible that White should have sufficient compensation for the great material sacrifices he has made, but Black's position is extremely uncoordinated and his king has no safe place anywhere on the board. According to the present state of opening theory, attack and defence are equally balanced, but... everyone is holding their breath for future developments."
Here's Radjabov-Karjakin (1-0) from 2006 that helped make 10.e5 be the most popular line for a few years again (source: http://www.chessgames.com/perl/chessgame?gid=1433642)
[FEN ""]
[Event "Cap D'Agde"]
[Site "Cap d'Agde FRA"]
[Date "2006.11.02"]
[EventDate "2006.10.30"]
[Round "3.2"]
[Result "1-0"]
[White "Teimour Radjabov"]
[Black "Sergey Karjakin"]
[ECO "B97"]
[WhiteElo "2729"]
[BlackElo "2672"]
[PlyCount "65"]
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bg5 e6
7. f4 Qb6 8. Qd2 Qxb2 9. Rb1 Qa3 10. e5 dxe5 11. fxe5 Nfd7
12. Ne4 h6 13. Bh4 Qxa2 14. Rd1 Qb2 15. Qe3 Bc5 16. Be2 Nc6
17. c3 (17.Nxe6!! { White could have played this } Qb4+ {forced} 18.c3 Bxe3 19.Nc7+ Kf8 20.cxb4 Rb8 21.Bg3 {with the threat of e6}) Qa3 18. O-O O-O 19. Nf6+ Nxf6 20. Bxf6 Nxd4 21. Rxd4
Bxd4 22. Qxd4 gxf6 23. exf6 Qa5 24. h4 Kh7 25. Bd3+ Qf5
26. Re1 Rg8 27. Kh2 a5 28. g4 Qxd3 29. Qxd3+ Kh8 30. Re5 Rxg4
31. Rh5 Rg6 32. Qd8+ Kh7 33. Qe7 1-0
Here's a Stellwagen-Anand, 0-1 in 2009, in the 10.e5 variation. The early queen sacrifice is long-known theory, technically 17...Ra4!? is the first new move of the game but it's unclear how much was preparation. 38...Kb8?? could have thrown away the game to 39.h6!, later 46.h6?? is also a blunder.
[FEN ""]
[Event "2008-2009 Bundesliga"]
[Site "Baden Baden GER"]
[Date "2009.03.28"]
[EventDate "2008.10.03"]
[Round "14"]
[Result "0-1"]
[White "Daniel Stellwagen"]
[Black "Viswanathan Anand"]
[ECO "B97"]
[WhiteElo "2605"]
[BlackElo "2783"]
[PlyCount "104"]
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bg5 e6
7. f4 Qb6 8. Qd2 Qxb2 9. Rb1 Qa3 10. e5 dxe5 11. fxe5 Nfd7
12. Ne4 h6 13. Bb5 axb5 14. Nxb5 hxg5 15. Nxa3 Rxa3 16. O-O
Nc6 17. Rb5 Ra4 18. Nxg5 Ndxe5 19. Rxe5 Nxe5 20. Qc3 Nc6
21. Rxf7 Ra5 22. Rxg7 Bc5+ 23. Kh1 Rf8 24. Qd3 Rxa2 25. h4
Ra1+ 26. Kh2 Bd4 27. Qg6+ Kd8 28. Rf7 Rxf7 29. Qxf7 Bg1+
30. Kg3 e5 31. h5 Nd4 32. Qf6+ Kc7 33. Qxe5+ Kb6 34. Qd6+ Ka7
35. Qc5+ Kb8 36. Qd6+ Ka8 37. Qd8 Nf5+ 38. Kh3 Kb8 39. Ne6
Ra3+ 40. Kg4 Nh6+ 41. Kf4 Bh2+ 42. Ke4 Nf7 43. Qf8 Nd6+
44. Kd4 Ka7 45. Nc5 Ra5 46. h6 Bg1+ 47. Kd3 Bf5+ 48. Qxf5 Nxf5
49. h7 Ra3+ 50. Nb3 Bd4 51. Ke4 Bh8 52. Kxf5 Ra2 0-1
Edit: crap, I didn't realize the PGN viewer doesn't show comments. I only had a few, but they don't show, sorry.
If blacks knows this variation well, and white does not know it well, then black can grab the pawn and keep it to the end. As Fischer said, "a pawn is a pawn is a pawn".
The idea is to grab the pawn, survive the opening, then end up in the middle game with an extra pawn. Once Black manages to survive the opening and develop, then he will actually be better.
Since this involves sharp variations, it is only played by those who know it well. It is not played much any more at high level.
There are few books on this variation.
Let's try to understand the position after ...Qa3 (see below). First of all, the name itself (Poisoned Pawn) already indicates that black should be careful in this variation. Let's look at the material balance: black is one pawn up. Next, looking at the King safety, the black king is slightly less safe because the white pieces are more actively placed.
[FEN ""]
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bg5 e6 7. f4 Qb6 8. Qd2 Qxb2 9. Rb1 Qa3
What should black look out for / aim for? Well, the Qa3 is not perfectly placed. The queen is better placed on c7. The queen might also become trapped. Black should focus on king safety and queen safety. Probably try to castle kingside, Bf8-e7, O-O. As well as Qa3-a5-c7. White should aim for launching an attack on the black king. The e4-e5 advance is one option, f4-f5 is another option, Bxf6 gxf6 is a third option.
White aims to keep all the pieces (avoid exchanges) and keep the black king unsafe. Black aims for king and queen safety and for exchanges of pieces that do not lead to static (pawn structure) weaknesses. I think that black should stay active and launch a counter-attack when needed. It is not unusual for Sicilian Najdorf positions to become very sharp and for the black king to stay in the center. The player with the black pieces should be ready for such positions and handle them as well as possible!