Whenever you waterbend, earthbend, firebend, or airbend, draw a card. Then if you've done all four this turn, transform Avatar Aang.
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Flying
Spells you cast cost 
less to cast. (This can reduce generic costs.)
At the beginning of each upkeep, you may transform Aang, Master of Elements. If you do, you gain 4 life, draw four cards, put four +1/+1 counters on him, and he deals 4 damage to each opponent.