How does UD deal with Impervious?

I'm running a UD/FW split with Soulreave but i'd like to drop it for another FW spell and considering the current composition of the deck I can't drop any of my UD spells to do so.

I'm wondering if any more experienced UD players could suggest some runes that could perform the same role as Soulreave. I have plenty of alt damage so counters to things like Impervious are what i'm really looking for.

 

Stitched Shaman - Dispelling Blows/Essence Capture - 70Nora
Demon Lich - Cleansing Flame/Swarm - 78 Nora
Minotaur Stoker - Flame Siphon/Initiative - 69 Nora

 

I was kinda hoping for a spell or something else that could be used on the spot to be honest. I'm in a tricky situation where i'm tight on room and keeping the bg at 15/15 is constantly a struggle.

 

Purefire?

 

Now we are talking, could be a little inefficient since i have no fire damage but it would serve the purpose. Thanks!

 

corrupted cultist, collection of souls or other LOL?

 

Retribution works, as a huge LoL hit.

 

Unless something has changed in a recent patch Ret deals Magic damage.

 

oops... I always thought of it as LoL for some reason