You know me, I just don't know when to quit!

I've been having some ideas, so I thought I'd share one of them and see what you think (the title is obviously a stop-gap - it's just a thesaurus job on Enduring/Abiding):
Eternal Evil ![Sauron [Sauron]](https://lotrtcgdb.com/forums/Smileys/classic/sauron.png)
Event • Skirmish
(You choose the value of
. Except when you play this card, its twilight cost is
.)To play, exert 2 minions (or spot a
![Sauron [Sauron]](https://lotrtcgdb.com/forums/Smileys/classic/sauron.png)
minion)
Make a companion strength -X.
So what do you think of this idea? The point is that it's a Shadow card that you can spend however much you want on, or however much is available. It's inspired by the X costing cards in MTG. Obviously in LotR an
![X [X]](https://lotrtcgdb.com/forums/Smileys/classic/x.png)
cost only works for Shadow cards (because FP can add an infinite amount of twilight), and you could attach other costs to the card, like "To play, exert a
![Sauron [Sauron]](https://lotrtcgdb.com/forums/Smileys/classic/sauron.png)
minion" or something.