I just wondered: can K + 2 nightriders force a mate against bare K? (A nightrider can make an unlimited number of knight moves in any direction - it cannot change direction partway through its move.)
The Wikipedia page on the Nightrider contains an example from T. R. Dawson, published in the British Chess Magazine in 1925, where a king, knight and nightrider force a mate against a lone king. I guess a similar procedure would work for two nightriders, but you have to be a little more careful to avoid stalemate.
See my book Fairy chess endings on an n x n chessboard (2017), p. 345 and 414. The ending of king + two nightriders against bare king on board 8x8 is won for the stronger side and the longest win has 22 moves. Also the ending king + knight + nightrider against king is a general win, see page 395.