In the case of demon’s and D’Orcs it essentially defines the fuel tank…to some extent
It’s building the body and innate abilities (lightning tail, claws, teeth, hide) plus the fuel tank in a case like Tom’s
For the most part at least. We have to keep in mind that the vast majority of summoned demons don’t have spell casting abilities and so the “fuel tank” is used to power innate abilities. E.g. breath weapon, incubus abilities, innate fear.
The innate fear thing is basically a fear spell if we were in a game.
In the case of holy beings, they radiate an “awe” spell
Saints, however are are bit more standardized since there are no surprises like Lenamare got.