'Is The Game of Nemoroth a Chess Variant?' I believe it is, though it
stretches the boundaries. For me, the telling point is that there's a kind
of checkmate (provided by compulsion).
Because the basic condition of victory is stalemate, and because the pieces
all have different moves, it would also stretch the boundaries to call it
an ultima variant.
The complexity of interactions of the pieces feels a bit Ultima-ish,
though.