It is a low cost of two ink, or a character of cost two or higher can be exerted to sing for free
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of Emet-Selch of the Third Seat's first ability)
Congratulations, your sealed deck is now ready to play
Maui works in Ruby/Sapphire and Ruby/Amethyst quite nicely and opens up other ink combos
Now that you have a creature that can naturally have 10,000 power, a cute reference to its attack from the Final Fantasy games, what do you do with it
Terra will be a fine, grindy commander for midrange decks, and I look forward to seeing how it develops