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Well, I wouldn't know about that, and I also doubt the statement that this game would be 'always won for black'. (That would make the Ghost significantly more valuable than a Pawn, as Pawn odds at worst reduced your score against an equal opponent to ~30%.) I can comment on the puzzles coined on this page, however: KNNKG seems a general draw. At first glance this is a bit surprising: KNNK under rules where black can pass his turn is generally won. The trick seems to be that the Ghost can hinder the Knights in going where they have to go to drive the black King to the corner. It throws itself into the path of the Knights like a kamikaze, knowing that it cannot be captured because KNN is always draw. It needs a certain agility to be able to hold off the mate; a non-capturing Dragon Horse (RF) is not strong enough to prevent a general win for the Knights, but a non-capturing Queen is enough to let the number of wtm wins drop to below 30%. KRKG is in general a draw; when the black King is already driven back to the 7th or 8th rank, however, it seems winnable.
Well, I will see if I can play-test it with Fairy-Max. It seems a very expensive piece, in terms of branching ratio. I guess that to not explode the search tree, I would need to apply extra search-depth reduction to Ghost moves. I see that there was a proposal to rename the piece. The name 'Journalist' suggests itself. Going everywhere, and getting in everybody's way! :-)
To get a reasonable value for the gost I had to adapt the way the Diagram calculates piece values; the usual formula M*(33+0.7*M) for a piece with M moves values it more than a Queen even when I do count non-captures only for 1/3 (and captures for 2/3) as I did. But it turns out that (0.11*N+0.89*C)*(22+0.7*N), with N the number of non-captures and C the number of captures, gives exactly the same result when C = N (as it is for non-divergent pieces), and puts more emphasis on captures. And it still predicts the same devaluation when a piece with 24 moves gets one captures or non-captures removed, from which I concluded that captures were worth twice as much as non-captures.
This still predicts a value of about a Rook, though. I guess the problem here is that non-captures contribute a lot through future mobility, where you can go after 2, 3, 4... moves. But for a Universal Leaper this provides no extra value, as it can get anywhere in a single move anyway. I now made the hack to discount the number of non-captures above 1/3 of the board area by a factor 10. That still makes the Ghost worth more than a Pawn. But some comments below claim it is worth more than Betza thought, so perhaps this is correct. In any case the Diagram would not sacrifice a minor for the Ghost now.
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