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
Commander Decks Battle your friends in a race to the hidden core
Im sure you could go to town and come up with a bunch of better choices for your ICC, right
This was likely due to Dagger already filling a similar role to her in the set, with an effect that influences Saga Creatures, aka, the summons of the set
this allows them to evolve a non-Floodborn character into their new form, for a reduced cost to play the Floodborn card as a bonus
Read More: The best Dragons in Commander The 10 best group hug cards for Commander There are so many good cards for this kind of strategy, if you can call it that