I know how DC is calculated, but I can't find anything specific on how the saving throws of monsters are calculated? What's being compared to DC when a player casts a spell on a monster? I'm assuming their CR has something to do with it. Do they each have their own individual fortitude, reflex, and will stats or is it by type or sub-type? Is there any public data on specific values? Is there a reliable rule of thumb for player spell DC vs monster CR?