Horseback Sipahi

As long as you control another red knight,
Horseback Sipahi gets +1/+1 and has haste.
{3}{r}, tap another X non-red knights you
control: Attacking red knights you control
get +X/+X, gain trample and haste and
have "Whenever this creature deals combat
damage to a player, it deals X damage to
target creature" until end of turn.