Cloaking field

[KaiZen7th]

Here is my new idea:

Creating a Canopy tree (Destructible doodad) on a chosen location, and the tree has a passive ability to:
a) cloak close-by friendly units.
or
b) give close-by friendly units chances of evasion.

Thank you every person who helps me so far on creating triggers based on my ideas.

 

[Chaosium]

If the tree is pre-placed in your map, you can create a region near it, then detect when units enter this region, and you have some dummy caster use a spell based on Invisiblity on them. Similarily, if a unit leaves this region, you can remove the specific invisibility buff.
Same concept with evasion, but you can simply add the ability when a unit enters the region, and remove it when they leave.