you can use the tornado aura, stacking aura and reduces move speed addatively ie: a unit comes in range of 1 unit with 20% movespeed slow aura and then a second so its in range of both, that becomes 40% slow, its a base aura and it doesnt show a debuff, check for it in the abilities part of object editor
Create a spell based on slow. Give the ability to a dummy casting unit. Make the slow last 0.1s and make a trigger which creates a dummy caster every 0.01s to cast the slow on any units in range of a point.
I don't get you here. If you want a dummy unit to follow the affected unit, just for sake of slowing the affected unit, you might as well add a slow ability (Endurance Aura, Tornado) which targets self to the affected unit, or even order a dummy to cast Slow to them. No need all the fancy dummy movement triggering. Sides, if you're gonna use the Slow method, you only need one dummy unit for the entire duration of the game. Just reuse it to cast the spell over and over again.with your idea what i would do instead is creating a dummy unit for every unit that enters the map that is locked to the unit (always the same speed and told to move to the same location and if it gets more that 80 or so range move it back and set its action again) that can have spells added and taken that do different effects, it would double the ammount of units in game but it would create HUGE diversitablility for his map, something not to be discarded lightly
I don't get you here. If you want a dummy unit to follow the affected unit, just for sake of slowing the affected unit, you might as well add a slow ability (Endurance Aura, Tornado) which targets self to the affected unit, or even order a dummy to cast Slow to them. No need all the fancy dummy movement triggering. Sides, if you're gonna use the Slow method, you only need one dummy unit for the entire duration of the game. Just reuse it to cast the spell over and over again.
As mentioned, the easiest way, is to give Tornado or Endurance Aura to a dummy unit (a unit with no model), and place the dummy units into the map manually. Whenever a unit enters the vicinity of the dummy unit, they get slowed. You don't even need to trigger it.
Or am I not getting what you want here?