In the Standard Format, there are eight Basic Energy cards: A Note on Basic Fairy Energy Although Fairy Energy is also a Basic Energy card, Fairy Energy is not legal in the Standard format
Professional players carefully integrate these support cards to maximize deck efficiency
If you play it in Red/Green, where you have access to a ton of mana and are packing some heavy critters, the right three cards in the graveyard option can win you the game, and in your hand can also win you the game
The play pattern goes like this: you cast Taniwha and pass turn, then on your next turn you untap and Taniwha phases out, then on your next turn Taniwha phases back in and your lands phase out, on your next turn Taniwha phases back out and your lands phase in, etc
Having access to exiled counterspells and removal can also be handy in a pinch