Mythra, Light of The Aegis

Haste,Flash,First strike,Vigilance
{w},{t}: Gain 5 Life
{w}{w}{w}{w}{w},{t}: You gain 15 life
If Pyra, Flame of The Aegis is in your hand, you may replace this card with it.
Smash attack(Arrow Storm)-{10}: Deal 5 damage to up to 2 targets. You gain 3 life. Create a 5/5 Legendary creature token with vigilance called Rex. If there is already a Rex creature token in play, put 5 +1/+1 counters on Mythra, Light of The Aegis.