The Monster Pack is the eponymous object that is the focus of the show.
Ollie is the Protector of the Pack, a position he inherits from his missing father.
In Sister Save Me, Ollie’s sister Pyper also becomes its temporary protector, Cho-Sub.
Backpack[]
Monster Pack
This is a Bag, the protector of which is Ollie himself. Judging by Trio's a Crowd, only the Chosen One can open his Magical Bag.
There were seven Chosen Ones before Ollie, as we can see in the Theme Song. Each of them corresponded to different periods in history, although Ancient Rome for some reason comes before Ancient Egypt.
Stone Age -> Roman Empire (Antiquity) -> Ancient Egypt -> Middle Ages (Viking) -> Middle Ages (Pirate) -> New Times/Civil War (Cowboy/Warrior) -> Modern Times (1st generation; Mr. Allen) -> Modern Times (2nd generation; Ollie)
Cho-Sub[]
When the Chosen One is wounded or injured, and if due to this injury they are unable to perform their duties, they will need a substitute. However, they are given a different bag — all they have to do is pull the dark-green T-shaped thing under the left strap of the Monster Pack itself, and a belt-bag will jump out of it, which looks exactly like the Chosen One's bag. The Cho-Sub is given their power for one week. The Cho-Sub’s bag itself chooses its own Cho-Sub — if the person does not suit it, it gave them heavy electric shocks until they take it off.
