You know what’s funny?  
I am writing a Homebrew DnD campaign in the Poniverse, and this is actually one of the spells I added in the game. Though I didn’t think of Crystalmancy…  
Anyway, this spell would send out a massive line of crystals like this one above.
 
Roll 1d20 to cast. Over 18 adds 1 extra damage to each damage roll. A perfect 20 instantly kills any target except for any boss.  
The spell does 3d8 damage in a 2 meter AoE range
 
THE DAY I finish this spell, I come over here and see this picture

“In Equestria, the gems seek you out!”