How to make a passive slowing ability?

[RobertMKD]

Hi all, I'm not sure this is the right forum for this thread, apologizes if it isn't, I'm new.
I have a problem, I'm making a GREEN map and I'm almost done with all of the buildings, I just need help for this problem of mine. I want one of my buildings to have a slowing effect on its attacks (to slow targets' movement speed by a percent). It is easy, I can just add "Frost Attack" to the tower and I'm done, but I want the percent of slowing to increase after each upgrade of the tower (10levels).

So, I need to make 10 abilities that will be added to each tower level. (example: 1 level - 10% slow, 10 level 60% slow). But how? I've been searching for passive abilities with slow effect on targets, and haven't find any.

p.s. I used "Slow Poison" for a base since it has 'Movement Speed Factor', but it doesn't slows units' MS, that's because the base ability is meant to have damage per second effect, not ms slowing effect

HELP!!! :C

 

[LordDz]

Just use Night Elf Dryad's Slow Posion? It slows both movement speed and deals damage.

 

[RobertMKD]

Gee thanks man!! It worked!!

I used it before, but it didn't worked, dunno why...

 

[Crystalknoct]

I made my necromancers have a passive aura that slows nearby enemies movement and attack speed by x% while they are within the radius I know you may not use it but I made it using. (Slow Aura: Tornado)