Elder Dragon because you have to choose a Legendary leader for your deck (such as the Elder Dragon Legends from the original Legends expansion)
Season of Growth's last ability triggers when you cast a spell that has multiple targets, as long as at least one of those targets is a creature you control
Let's talk about that
While this may sound difficult, Najeela, the Blade-Blossoms token-generating ability will give players access to exponentially more creatures each combat
Many years ago, we made a set called Innistrad where we introduced double-faced cards
Since its in GW, the decks have access to Giant Growth, Berserk, Crusades, Jihad, Army of Allah, and such to further buff this critter