Aang, Bending Adept

Vigilance, Flying
Aang, Bending Adept is all colours.
Multicoloured spells you cast cost {1} less to cast.
Whenever you cast a multicoloured spell, you get
an experience counter.
At the beginning of the endstep, if you have four
or more experience counters, you may transform
Aang, Bending Adept.