Azula, Ruthless Firebender (TLE-101) [Avatar: The Last Airbender: Eternal-Legal]

Firebending 1 (Whenever this creature attacks, add R. This mana lasts until end of combat.)

Whenever Azula attacks, you may discard a card. Then you get an experience counter for each player who discarded a card this turn.

2B: Until end of turn, Azula gets +1/+1 for each experience counter you have and gains menace.