I took a look at Angel Arena's version and it looks like way too complicated and also not efficient at all. You need to learn about JASS to do something like that.
You can use just one global to do what you want: hashtable. Using hashtable you can handle everything.
Basically you'll need to log all units through an event player unit attack, check if the attacker has the desired item, save data into the target unit, use a MUI (Multi-Unit Instanceable) timer, etc. I made an item version, look:
- Every attack increases the damage by 20%;
- If you don't attack within three seconds, it resets.
Is that what you wanted?