Poison Aura

I just want to know what i can use as a base ability for a poison aura.

Basically, the unit learns the ability and from then on causes xxx damage per second to enemy units within a range.

I've tried a few things like, Poison Spears but it doesnt work.

Disease cloud ?

fully custom on jass maybe ? or what you want ?

Permenant immolation?

unholy aura?

uh ya disease cloud and permanent immolation should work buddy. depending on whether you want it to "spread" or not.

I want it to spread. What im doing is this.

I use the phoenix fire ability to auto fire on units within range.

I detect the attack and each time check if a player has a specific buff.

If i find that buff, i then create a unit and make it follow the attacked unit. This unit thats created i want to be able to emit a poison aura for about 5 seconds.

So which should i use?

Disease can't kill a unit but it can do damage over time.
Immolation can kill a unit but can't do damage over time.

Choose whichever fits your spell best.

First in my head flies Vex's aura-template. But I found some issues, like 2 heroes having a positive ability and sharing the range of each other's aura will result in not having the effects on any unit anymore in the game, if the unit move out of the range of each other.

1st reply says it all...
Desease cloud and desease cloud again(I think it should be as it is, just drain, not kill). Anyway, if you wish to kill units replace it with immolation or change the second desease cloud's damage type somehow.
The buff will stay with the unit for the specified duration when it leaves the AoE of your hero's aura. If you wish you can also create a dummy unit to follow that unit, so it appears that it too has this aura(probably with lower stats).

Permanent Immolation should work fine. Unholy Aura with negative HP Regen and unittypes Enemy should also work fine. Although logically they are the same, I just think Permanent Immo is fine and you wouldn't need negative values for it.

Negative regeneration is not considered damage, so bounty and exp are not given if the unit dies from it.

Maybye something like shadow strike on units in range of the unit with the aura without the SS-buff, then shadowstrike on units who comes in range with that unit again, and so it goes on? (instant shadowstrike hit and no missile of course, and a more "disease"-like effect.)

Hey, that's if 2 units have the same aura? Then I guess it is a good application for stacks.