Event - unit enters region x
action -- deal x damage to unit (I don't remember the exact wording because i don't have WE installed anymore. I believe the damage thing is in generic or specific unit events.)
Make sure you have the region.
cheesdude,I believe Rethon was talking about damage over time, or damage per second. In that case, your trigger won't work since it's instant damage.
To Rethon, this trigger is actually pretty simple but in my way you'll use 2 trigger instead of one. The first one is the "enter the region" thingy, I'm pretty sure you've known that already.
The second trigger, first you should create a variable type "Unit Group" (not an array) and name it "BurningUnit" or whatever you want. That group will determine which unit is burned and which is not.
Now back to the first trigger, in the action part, do it like this: Unit Enter Region ---> Action: Put that unit into the unit group you just created ( i don't have WE right now so you'll have to find it out yourself,
)
Again with the 2nd trigger, this is what make your unit take damage, do this:
_ Event: Every 1 ( or else ) second of game time ( the Periodic Event thingy )
_ Action: Unit - Set [unit match condition [belongs to the BurningUnit Group]]'s HP to [Current Hp - [damage]]
Or an alternative action: Unit - Cause [some unit] to deal [X] damage to [unit in the BurningUnit Group].
There you go then, any unit enter the region should take some damage every second. Sorry for some confusions cause by the lack of WE.