If you control a commander as you cast this spell, you may choose both instead.* Creatures you control gain flying, vigilance, and double strike until end of turn.* Creatures you control gain lifelink, indestructible, and protection from each color until end of turn
His second ability is very niche and won't really ever be relevant, but in the pirate deck, as a 5/4 for 5 with Rush and the ability to ready himself, he'll be solid
They're equally satisfied by an artifact you sacrificed to pay a cost, a creature you controlled that was destroyed by Sephiroth's Intervention, or an enchantment you returned to a player's hand with Cryptic Command
Hopefully Dockside Extortionist's reprint in Double Masters 2 will bring down that cost a bit.
I like Wildest Dreams for its pleasant mix of power and flexible cost, and I think it will be better than Regrowth for this deck while still being basically Regrowth when that is all you wanted it to be
This mechanic seemed a little slow to me during spoiler seasons, but it plays a very important role in the format