Ok... I'll try this a little slower.
You base the skill off Mass Teleport but you give it three levels. Now, let's see the triggers once again.
Event - An unit starts the effect of an ability
Conditions - Ability being cast equal to (Yourability)
Actions - If (Level of (YourAbility) for (Triggering Unit) is Greater Than 1) then do Unit - Make (Triggering Unit) Invulnerable)
The Event/Condition are pretty clear, right? Now... As for the if, you can find the if condition at Integer Conditions. Search for (Level of Ability for Unit), changing Ability to the Mass Teleport Ability you made and Unit to (Triggering Unit). As for the invulnerable stuff, search at all unit actions for an action Unit - Make Invulnerable/Vulnerable. Set the unit to (Triggering Unit) and the state to Invulnerable.
Let's go to the second trigger.
Event - An unit stops casting an ability
- An unit finishes casting an ability
Conditions - Ability being cast equal to (YourAbility)
Actions - Make (Triggering Unit) Vulnerable.
The action is the same one above but you just change hte Invulnerable state to Vulnerable. Hope it helped you more this time!
~Daelin