I'm really intrigued by the new Ashiok card but it has a lot going on. This is a card with some synergy with paying life and let's you exile that many cards from the top of your library so long as your library has that many cards in it.
This is all about exiling cards and making the nightmare tokens larger. So, sure, have some cards that require paying life but don't get too crazy. You still need to balance paying life with exiling your library. And yes, read that static ability clearly, there is no may clause in there. You do exile cards from your library instead of paying life... as long as you have that many cards in your library.
The static ability reads as such:
If you would pay life while your library has at least that many cards in it, exile that many cards from the top of your library instead.
And the loyalty abilities:
+1: Look at the top two cards of your library. Exile one of them and put the other into your hand.
-2: Create two 1/1 black Nightmare creature tokens with “At the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature.”
-7: Target player exiles the top X cards of their library, where X is the total mana value of cards you own in exile.
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So now you can use those crazy spells that require life payment as long as you understand you'll be exiling your library. Maybe find some spells that let you retrieve cards from exile. After all, the Nightmare tokens get +1/+1 counters so they would keep their stats if cards were to leave exile.
In the meantime, Plunge into Darkness is looking pretty good. It's $3.75 right now.
