Just wanted to note that this spell can't be cast if there are no creatures in play. That seems odd... especially since I'd totally play this targeting myself and an opponent if it meant it would win me the game.

Ok, ?

I think jmg is suggesting making the second ability "to up to one other target creature."

Alternatively, "Choose target creature or player and up to one other target creature. ~ deals 2 damage to each of them. Shuffle ~ into your library."

Alternatively alternatively, why allow the first one to hit players but not the second one? Just make the second one "to another target creature or player." In fact that's probably actually what jmg was suggesting.

Is 2 x 2 damage fair at RR? for instant?

Well, it's reminiscent of Arc Trail, which was very good as an uncommon sorcery at . This is more damage but it's rarer and colour-intensive, so it's allowed to be pretty good.

This would likely get played in constructed decks, but that's fine - some cards have to, after all ;)

ok then 2 and may 2 it is.