Avatar, the Last Airbander

Flying
Elemental Ascension (At the beginning of your upkeep, you may pay the cost for the next level. If you do, it gains the ability of that level.)
Level 1 - {1}{u}: This creature has hexproof.
Level 2 - {g}: Whenever a land enters the battlefield under your control, put a +1/+1 counter on this creature.
Level 3 - {1}{r}: {t} This creature deals damage equal to its power to any target.