[Spell] Burn on Hit

[Faith]

I know there is an ability that would allow me to make a hero burn any units it attacks without being an active or autocast.
I need an upgradeable passive, and I can't think of the name of the ability to base it off of.
If anyone could pass me the name, I'd be very grateful.(;

 

[ap0calypse]

Would a modified poison-ability do the trick?
It's a passive spell with an on-hit DOT and can be upgraded.
Aside from that, I can't think of anything either.

 

[Faith]

I found what I was looking for, it was Burning Oil.
All I did was remove the area of effect, and I'm hoping it will work!
Although, modifying the poison passive-ability would probably have been easier..

 

[jrhetf4xb]

You could also try Liquid Fire, just modify Targets Allowed so it doesn't affect structures.