A friend of mine is wanting to do a specific build and as far as I am aware you cannot apply a modifier multiple times in this way. Can someone confirm if this is a RAW legal tactic?
level 6 tiefling celestial warlock, with 16 charisma (so modifier of +3).
Cast shillelagh to make staff 1d8+cha [source: pact of the tome]
Then cast searing smite for 1d6+cha [source: tiefling and celestial warlock's radiant soul feature to add charisma mod]
Then green-flame blade attack for another 1d8+cha [celestial warlock's radiant soul feature to add charisma mod]
A single hit would be 2d8+1d6+9
Do all these instances of charisma modifier stack like this?