Some procedure triggers like "when entity hit with item", "when mob/player collides this entity", "when player hit with bullet" could use two entities as dependency rather than just one.
For example, in the "when entity hit with item", the "user" is the player that uses the item and the "target" is the entity hit with the item. This way it would be possible to do something like this:
(When mob/player hit with item:)
If has (user) in inventory item (mana)
Add potion effect (poison) to (target)
Remove item (mana) from (user)
Of course these dependencies could only be used with compatible triggers, like the others. Otherwise they will simply stay "entity" like default.
This isn't very important but would make events more dynamic.