Increasing damage dealt to Hero

It's been awhile, hope everyone is still doing OK!

Anyway, I've been messing around with an Enfos map to try to get the end game a bit more interesting. One of the items I have created gives melee a small cleave; but seeing as how overpowered that would be late game I'm trying to throw in a negative effect.

Basically, every 15 seconds there's a chance that the wielder will over exert himself and lose 95% attack speed/movement/damage. Which I have already done. However, I'm finding that this isn't enough to balance out the item the way I want, and I want to increase damage taken during those 5 seconds by 25%.

How would you guys go about doing that? I've been out of the loop for so long and I know this is a dumb question! My current idea is to give the hero a dummy berserk and activate it then remove it, however that just seems clumsy and I'm sure there's a better way. There's probably a spell that increases damage taken, but I'm drawing blanks.

Thanks guys!

give the hero a negative armor buff? It may not increase damage directly, but depending on the map, may produce the same effects. You could also script a reverse shield system (where you detect damage events on the unit and cause 25% damage dealt per attack [100% + 25% = 125%]).

Well if you've ever played DotA, The Orchid Malevolence is sort of the perfect example I'm looking at.