Ability costs can include ink (paid by exerting cards in your inkwell), exerted cards (paid by, well, exerting cards) or something else explained on the card itself
Always pack enough cards to fill your inkwell : If you dont have enough characters, or abilities, to create a strong ink-well pile then youll eventually be outpaced by your rival
CEDH decks exploit this by dropping stax pieces, like Magus of the Moon and Thalia, Guardian of Thraben, but you could also cheat in big bruisers like Captain of the Watch
Bestow a Gift Action Between this card and the Mama Odie revealed earlier, I see a theme arising
Also, for an additional cost of one of each mana type, you may untap all attacking creatures, giving them trample, lifelink, and haste until the end of the turn, and trigger another combat phase