So.... which game should I burn my money into?

Why not both?

Because money? The fact that the question was asked kind of implies that both isn't an option.

So what are we supposed to work with here then? OP gave literally no indication of their taste in games or what they're looking for.

I don't know, but I don't see how that makes "both" a helpful answer. ;)

Nine Parchments is a Frozenbyte game, so it might see a day one release on GOG. Plus is a co-op game, so if you have somebody to play it with then that's surely a plus.

I know nothing about Mages of Mystralia.

To be honest I was just quoting that Old El Paso kid, but I can see how it might have been too subtle.

It totally depends if you are more into classic Zelda with Procedural Magic, or a co-operative blast'em up game of magic mayhem from Frozenbyte!

Anyway, at this point the choice is clear: Mages of Mystralia. Why? BECAUSE THE OTHER GAME ISN'T EVEN RELEASED YET.

Got that? Good. Didn't get it? Even better. Your life, your choice, Coca Cola.