Syncretic Holy Magic

Using your Deep Knowledge on both the Holy Rites and the ways of Magic, you have formulated a way to fuse both into a single cohesive whole. Granting you the following:

Theurgy Fusion. Your Spell Saving Throw DC, and Spell Attack Modifier now gains an additional bonus. Choosing between Intelligence, Wisdom, or Charisma. Dependent on your current Spell Casting Stat Modifier, as that Spell Casting Stat Modifier cannot be chosen twice.    
For Spell Saving Throws is 8 + Original Casting Stat Modifier + Your Proficiency Bonus + (New Casting Stat Modifier/2)   
For Spell Attack Rolls is 1d20 + Original Casting Stat Modifier + Your Proficiency Bonus + (New Casting Stat Modifier/2)

Sensory Mix. When Rolling either an Arcana or Religion Check that implicates both forces at the same time, you will have advantage when rolling.