Arwen, the Fallen Angel

{t}: Each opponent loses 1 life and you gain that
much life.
Whenever an opponent loses life, put that many
+1/+1 counters on Arwen, the Fallen Angel.
If Arwen has 5 or more +1/+1 counters, she
gains flying and has "whenver this creature
attacks, each opponent discards a card, then loses
life equal to that card's mana value".