p.boxed
  | Any piece guarded by a friendly knight can also move like a knight.

p.
  In addition to its normal abilities, a piece guarded by a knight can move like him.
  On the following diagram, 1.Nf4 would checkmate because it guard the g6 queen.
  If it is black to play, then 1...Rxe2 is possible due to the c8 knight.

figure.diagram-container
  .diagram
    | fen:7k/8/6Q1/1n6/8/2r5/4N3/K7:

p.
  A pawn on the sixth rank guarded by a knight could thus make a knight move to reach
  the last rank and promote.

p These oddities excepted, orthodox rules apply.

h3 Source

p
  | The original rule invented by Mannis Charosh (1972) is described for example 
  a(href="https://www.chessvariants.com/diffmove.dir/nrelay.html") on this page
  | . However, I don't really like the invulnerability condition and the restrictions
  | imposed in these rules, so I implemented this simpler version.