[TUTORIAL] How to summon vanilla entities with custom tags (which can be used in procedures)

-You need to summon the entity with a command which goes "/summon your entity ~ ~ ~ {Tags:["name of your tag"]}

The tag I used here is called "magic", as you can see. The trigger in the second picture is just an example, it is not strictly necessary to make the system work Avoid using a tag named after the entity you're working with, that may prevent the whole system from functioning at all. 

In the second picture the command runs in the name of Event/Target entity, which is the entity we're going to check the tag of; it may vary depending on the role assumed by your entity inside the procedure. You can adjust the command as you please to target whatever entity you need to check the tag of.