unholy frenzy: targeted to nontargeted?

i want unholy frenzy to become a hero ability that increases atttack speed in exchange for taking damage per second. easy enough, that was done quickly. however, i also want it to only be castable on the hero himself. by changing targets allowed to self only, that was accomplished. so what i have now is an ability that asks for a target, and the only applicable target is the caster himself.

but... is there a way to make it a nontargetable spell, to make it an ability such as berserk?

triggers with a dummy spell

Sorry, but you can't change aspect of a spell that doesn't originally support it. It might be possible via slk, but your gonna have to stick with it being self target. Just like Ry's Bl based ability.

With triggers, make the actual spell he has a dummy spell. base it off berzerk or some stuff with no stats.

Make a trigger, make it so when the trigger is activated (dummy spel is cast) an invis unit spawns, which then casts the ability you want on the hero, and then remove the invis unit.

Use a Hero Skill Level Compairison to determine which version of the skill the invis unit casts.