Double Demon Fang

You swing your weapon twice in quick succession causing two waves of blue arcane energy to erupt from your blade with significant force that foes hurtling against the ground in a line to the target. The target must make a Dexterity saving throw which if failed the target takes 2d6 force damage and is knocked prone or they take half on a success and are not knocked prone. 

Prerequisite: must know the demon fang cantrip already before learning this spell. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 2d6 for each slot level above 1st.