An extremely simple trigger, something a beginner could most likely make by themselves.
However, you wouldn't believe what some people on TheHive have trouble with, so this can be extremely useful.
The only problem with this is any time any unit enters the area it will make him invulnerable.
In order to make a specific unit invulnerable, you would use the condition
Triggering Unit Equal to (UnitYouWantEntering)
In order to make only 1 unit invulnerable, you could add the "Turn Off (This Trigger)" action.
You could also combine these 2 to make a specific unit invulnerable only once.
An alternative to making units invulnerable would be the simple action of Unit - Vulnerable/Invulnerable. Or for a group. Unit Group - Vulnerable Invulnerable.
Good luck, and thanks for the tutorial steven.
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