This spell can only be MUI if you use "A unit Starts the effect of an ability"
Trust me.
Nice idea btw

...
The truth: Your spell is too simple to be uploaded here

Try to make something cool

If you want to improve the spell, you could add a lot of configurables (ex: damage, effects, hp payment, knockback boolean, optional knockback trigger, ...)
You should make this spell worthwhile.
Henceforth, i shall give you a 1/5 and vote for rejection

I'm sorry...
I gave you some ideas to help, so i hope you can fix this spell, because it would be really awesome with a little work
Good luck
PM me if you need any help with triggering (i don't write others' triggers, but i do help when it comes to leaks, MUI-bility ;p, efficiency, functionality.)

thanks for understanding (-.- unless you hit your computer and broke the screen in anger ;P)