About nasuverse layers, I'm not gonna bother with the authority stuff since that's more complex and more tiresome, so others can have fun with that, but I can at least try to make an argument about normal resistance of servants.
Servants, by default, are Divine Mysteries, beings of immense mystery, something that grants them a great deal of resistance in general to stuff, however, among several servants exist a certain skill specific of certain classess or individuals, the Magic Resistance skill, this skill is divided among ranks:
Rank E: The lowest possible Magic Resistance, it go from reducing the effectiveness of spells to completely resist weak magic.
Rank D: The point at which Magic resistance become more significant, as spell of low rank get completely resisted, examples include Archer resisting spatial hax
An example of hax getting resisted by this Rank include Archer resisting Medea
spatial hax.
Rank C: At this point one resist spells of medium level.
An example of hax getting resisted by this rank is Medusa petrification most of the time not working against those with
MR Rank C, or Violet Crack Ice which
need MR Rank C to get resisted.
Rank B: At this point people is
basically immune to anything besides high thaumaturgy and grand rituals, and even those have problems affecting someone with this rank.
Rank A: No modern magecraft is able to affect this rank, only things from the age of the gods can hope to affect it.
Rank EX: Distinction between spell ranks are meangless, except from powers directly from gods the rest of stuff get resisted.
Besides this basic layer stuff with servants and magic resistance people can also make arguments for layering o mystery, rank of mystic eyes (which should be straight forward with their ranks), authorities and other stuff, but again, I don't want to deal with that so if competent supporters feel the desire to argue for them then please go ahead, though I'm uncertain if they will do it as they don't tend to participate much in the wiki or care for this type of stuff.