This question already has an answer here:
- Do resistances stack? 1 answer
EDIT2: I just looked up the oath online, and it seems the confusion has been caused by a loss in translation. The wording in my copy did not speak of "granting resistance to damage from spells" but it said "taking half damage from spells" which is pretty close to the wording if you succeed in your saving throw against a fireball.
So this question is indeed a duplicate and can be closed and forgotten.
I know that stacking the same resistance accomplishes nothing.
But what happens when different resistances affect the same damage event?
Let's say the random evil warlock Doomdoom shoots a fireball at the bear totem barbarian Fuzzyface who is raging through his minions. But Fuzzyface is standing right next to Evl-b-gon who is a paladin that took the oath of the ancients.
Bear totem halves damage(=grants resistance) from pretty much all damage types, including fire. Which a fireball undoubtedly would deal.
The oath of the ancients aura does the same for spell damage. The fireball is without a doubt also a spell.
So, how much damage does Fuzzyface take?
RAW preferred, but RAI with an argument about why it is intended that way would be appreaciated as well.
EDIT: Apparently this is taken as a duplicate by a lot of people. While pretty similar, I do not think those questions ask the same thing.
There is no damage type "spell" in the game.
The barbarian has resistance to the damage type,
but the Paladin halves damage from a source.
Solving this with PHB 197 by accepting "spell" as a damagetype would effectively remove the benefit of the bear, since the damage types he gains resistances to will be almost always be caused by a spell.