Each one has a strong questing value that forces opponents to challenge or risk falling behind, and then once challenged and/or banished, their effects activate drawing you cards, forcing opponents to discard or return a character to their hand, and more
Usually its life, but the first card draw for black was something completely different, something they just dont do anymore
Like most Magic: The Gathering cards, the value of Omega, Heartless Evolution depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy)
Songs: A subtype of action cards, but can be played by Exerting one of your characters (turning the character sideways) to pay the cost rather than spending your Inkwell resources
Lastly, the quality of the cards from a given release, in context of Commander (obviously)