Any time you would gain life, you gain one more of that amount, which isnt a ton, but adds up over time
They can be played alongside high-cost cards in order to spend your extra ink and develop your board, they can get buffed by a Support character like Rolly and become a cheap way to trade up into bigger threats, and Lucky can discover them when you use his ability Good as New, making them more valuable in your deck than in your hand
Even if Blightsteel Colossus is countered or would be put into the graveyard through other means, it still gets shuffled back into your deck, making it an unstoppable force that can always come back again
Players can now have their characters "sing" the Song into play, fulfilling the required Ink cost (or even exceeding it) on the Song card
Dump all of your White Mage counters on this card, and youll be one-shotting opponents in no time
Your opponents can collude to weaken the impact