Reading through the features of the light domain Cleric I’ve discovered:
Corona of Light which states (Emphasis added):
Starting at 17th level, you can use your action to activate an aura of sunlight that lasts for 1 minute or until you dismiss it using another action. You emit bright light in a 60-foot radius and dim light 30 feet beyond that. Your enemies in the bright light have disadvantage on saving throws against any spell that deals fire or radiant damage.
Now the Aasimar race has subrace racial features that allow them to add radiant damage to any spell that deals damage, which causes that spell to now do radiant damage as well as their normal damage.
These features are: Radiant Soul and Radiant Consumption
Which both state (Emphasis added):
“You can deal extra radiant damage to one target when you deal damage to it with an attack or a spell“
So if you combine these two features you can cause any damage dealing spell saving throw to be made at disadvantage. As far as I know this all perfectly works RAW. What I want to know is if there is any rule (excluding adventure league rules) I am forgetting that would prevent me from using this combination in games?