The Yellow Knight Errant

Whenever the Yellow Knight Errant fights a creature, if the other creature dies, put a +1/+1 counter on the Yellow Knight Errant.
{1}{r/w}{r/w}, {t}: The Yellow Knight Errant fights
target creature.
{r}{w}, {t}: The Yellow Knight Errant deals
damage equal to it's power to target player or Planeswalker.