Considering greens ability to produce big creatures is unparalleled, you shouldnt have too much trouble getting a big beastie on the board so the Caryatid can help cast an even bigger beastie
FromTheShire: I'm absolutely mad for Planechase Commander, so seeing built in support in the precon decks is awesome
Whenever this creature deals combat damage to a player, draw a card if that player has more cards in hand than each other player
In lore, Betor is a Spirit Dragon that helped to free the Abzan (white/black/green) from its Dragonlord to gain freedom
She can give you oodles of mana easily, she can draw you cards, and she can synergize with many other untap effects to produce more mana than you know what to do with
Luckily, its all connected