Recently, a strange engine with a mysterious nickname "Mystery" appeared on CCC, there is no information about it except the most basic one. One of the strangest things is that at 'CCC 20 Rapid: Qualifier #2 (10|3)' it performed poorly. But at the same time, in a one-on-one battle with the "Berserker", it won confidently. And now beats "Ethereal", one of the strongest engines.

Is there any additional information about it? About its developers? And how can you explain such a different level of play? And it is not clear why, if the "Mystery" showed a poor result, it was put in a one-on-one battle with the strongest engines. Not that important, but it also doesn't have TB Hits.

  • Don't remember where I saw it, but the last time a mystery engine played in CCC, it was revealed to be a Stockfish fork - which would make sense, since there are very few engines capable of beating Ethereal.
    – Allure
    Commented May 19, 2023 at 0:55
  • 1
    As for why it performs badly in a tournament but does well in head-to-head, the first explanations that come to mind are 1) no contempt and 2) small sample size effects.
    – Allure
    Commented May 19, 2023 at 0:56

3 Answers 3


On July 13th, chess.com revealed Mystery as its new closed-source engine, Torch:

Announcing Torch: New #2 Chess Engine

Torch is a brand-new chess engine built from the ground up by top chess engine developers. The team is composed of: Andrew Grant (Ethereal), Finn Eggers & Kim Kåhre (Koivisto), Jay Honnold (Berserk), and Michael Whiteley & Dietrich Kappe (Dragon). Mark Lefler and Larry Kaufman have been advisors to the project.

Many on the team have long discussed joining forces to produce an engine capable of contending with the best out there. Through the support and funding of Chess.com, we have done exactly that. A single unified effort by our developers has allowed us to rapidly produce the new number-two engine according to Torch’s performance in the Chess.com Computer Chess Championship. Our goal is to be number one.

The development of Torch is supported by many open-source tools, including pytorch-nnue, Cutechess, and OpenBench. While Torch would not be as strong as it is today without these tools, the entire source code of Torch is an original effort with no code being used from any other engine.

Torch is not yet publicly available but will be made available to certain relevant third parties for ratings. It will also be available through Chess.com’s analysis in the future. The team hopes to bring new ideas to the engine to allow greater insights to be delivered to the chess community. Chess is an infinitely fascinating game, and our goal is to push further into the depths.

  • The Torch Team

According to Neil Wagner commenting on Silicon Road: Great Engine Middlegames! A second brush with Mystery! CCCC Mystery vs Koivisto Bonus:

Andrew Grant, the tournament director of CCC and author of Ethereal, seems to be the only one who knows mystery's true identity. He did clarify that it was not a dumbed down version of stockfish or dragon as that would be rather lame. It seems to be an older engine (Maybe laser?) with NNUE added to it but no tablebase support.


Perhaps a large language type AI involved in setting the neural net? With considerably more parameters? It's making so much progress that it can challenge Stockfish now. And it achieved this without end game table base.

At the moment Mystery is beating Dragon in their bullet match. Here is a short win from a French position where Dragon could only draw. Watch the brilliant knight manoeuvre from f4-d3-c5-e6 plus sacrifice that took Dragon by surprise: https://www.chess.com/computer-chess-championship#event=ccc20-bullet-challenger-match&game=136

This game lost on the table base though: https://www.chess.com/computer-chess-championship#event=ccc20-bullet-challenger-match&game=509 Repetition error by Mystery: https://www.chess.com/computer-chess-championship#event=ccc20-bullet-challenger-match&game=12

Looks like it would be easy to improve on it and give Mystery a big chance to win in the world computer chess championships.

Exciting for chess!

P.S. The secret is revealed here: https://www.chess.com/news/view/torch-chess-engine

But Stockfish is torching the engine formerly known as Mystery! https://www.chess.com/computer-chess-championship#event=ccc20-bullet-finals&game=283 In many cases because of wrong end game evaluation due to missing table bases in this early version of Torch.

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