At the beginning of your upkeep, Mayael's Aria triggers.
Holding priority, activate Targ Nar by paying , doubling its power and toughness until end of turn.
Repeat step 2 until Targ Nar has power 19 or greater.
Resolve the Mayael's Aria trigger, causing you to put a +1/+1 counter on each creature you control, gain 10 life and win the game.

The mana cost of the combo can be reduced significantly depending on what Targ Nar's starting power is. The cost listed above assumes Targ Nar has a power of 2. The costs for other powers above this are: for power 3 or 4; for power 5 through 9; for power 10 through 18; for power 19+.