A new spell/ability

A new spell/ability

was wondering how i would make the following spell:

Target a hero in melee range.
The animation is as if the blademaster just had a critical strike.
Instead it has a shadow strike like effect minus the arrow.
Except the numbers are red instead of green

pretty much with the idea that you maim the person and they're bleeding so they slow down.

Piece of Cake just go and create a new buff and change the model art file from the greenie thing you get on the target to some blood from the spawned effects, change the name from slow poison to maim or sum, and thats it, replace the buff in the ability and you got your self your maim thing.