The level 7 Oath of Ancients feature, Aura of Warding [Player's Handbook, pg. 87], gives resistance to all spell damage.
The spell Shadow Blade [Xanathar's Guide to Everything, pg. 164] conjures a weapon with the finesse and light properties, and deals 2d8 psychic damage on a hit.
If a creature wielding a Shadow Blade makes a normal attack against a paladin with the Aura of Warding feature, does that damage get resisted, or not?
Lets start with the quotes of shadow blade and Aura of Warding:
You weave together threads of shadow to create a sword of solidified gloom in your hand. This magic sword lasts until the spell ends. It counts as a simple melee weapon with which you are proficient. It deals 2d8 psychic damage on a hit and has the finesse, light, and thrown properties (range 20/60). In addition, when you use the sword to attack a target that is in dim light or darkness, you make the attack roll with advantage.
If you drop the weapon or throw it, it dissipates at the end of the turn. Thereafter, while the spell persists, you can use a bonus action to cause the sword to reappear in your hand. [...]
[...] You and friendly creatures within 10 feet of you have resistance to damage from spells. [...]
I have quoted all of the shadow blade spell primarily to demonstrate that it does a lot of things that a normal weapon would not. It is magical, you just are proficient with it, it deals psychic damage, it has advantage in dim light or darkness, it dissipates if dropped, and it can be summoned back to your hand. From these we can certainly establish that it has numerous benefits exclusively because it is from a spell.
Because it does all these things, I would consider damage from a shadow blade to still be damage from a spell, especially because the actual mechanics that determine how much damage is dealt are part of the spell description. I would contrast this with using a spell like creation to make a mundane weapon whose statistics would be found outside the spell description and would thus be wholly unrelated to the spell. For me, swords made with creation do not count as damage from a spell.
Because shadow blade is from a spell, and specifically because its exact effects are described within a spell, I would consider it to be damage from a spell and thus be reduced by Aura of Warding.
There are some semantics to unpack here. There exist numerous summoning spells, but in particular, there are the new ones from Tasha's where the mechanics of the summons (their stats) are defined within the spell description itself. I personally wouldn't consider damage from a summoned creature to be damage from a spell (similar to how attacks from summoned creatures are not magical), but this gets into the world of how many levels of abstraction away do we have to get before we consider something to no longer be damage from the spell.
What if a spell shoves somebody off a cliff? Or some sort of mind control results in the controlled creature taking damage? Or a summoned creature makes an attack? Or a sword made through creation is used? Or a shadow blade is used? It's all this semantic mess, so perhaps at the end of the day the real answer is that it's up to the GM.
This is a bit of a gray area, I would say. I think Medix2's answer is excellent, and if they were my DM I wouldn't object to their decision at all. However, in my opinion, a strictly literal reading of the spell Shadow Blade only creates a weapon and deals no damage. We can compare it to a very similar spell, Flame Blade. One huge difference is that when you attack with the weapon summoned by Shadow Blade you do a regular weapon attack, but Flame Blade says,
You can use your action to make a melee spell attack with the fiery blade.
The absence of similar wording in Shadow Blade solidifies my view that Shadow Blade only creates a weapon and that an attack with that weapon is separate from the spell, similar to how an attack from a summoned creature is not damage from a spell.
The reason for this is that the spell Shadow Blade describes the summoning of an item, and includes the description of what that item does for the sake of brevity, and to mitigate the need for a player to perform additional lookups of item statistics. This would be similar to how the Tasha's Cauldron of Everything spells designed to summon customizable creatures includes, as part of the spell description, a statblock that is clearly necessary to the behavior of the spell, but which describes a creature summoned by a spell whose attacks do not themselves constitute the damage of the spell itself.
Under this interpretation, we conjecture that the spell Shadow Blade behaves as though there were an item defined with the following attributes:
Shadow Blade
Simple Weapon, Melee Weapon
1 lb.
2d8 psychic + 1d8 when created with a 3rd (or higher), 5th (or higher), or 7th (or higher) level spell slot each
finesse, light, twilit, thrown (20/60 ft.)If you drop this weapon or throw it, it dissipates at the end of the turn. Thereafter, while the spell persists, you can use a bonus action to cause the sword to reappear in your hand.
A character wielding this weapon is proficient in it.
Finesse. When making an attack with a finesse weapon, you use your choice of your Strength or Dexterity modifier for the attack and damage rolls. You must use the same modifier for both rolls.
Light. A light weapon is small and easy to handle, making it ideal for use when fighting with two weapons.
Thrown. If a weapon has the thrown property, you can throw the weapon to make a ranged attack. If the weapon is a melee weapon, you use the same ability modifier for that attack roll and damage roll that you would use for a melee attack with the weapon. For example, if you throw a handaxe, you use your Strength, but if you throw a dagger, you can use either your Strength or your Dexterity, since the dagger has the finesse property.
Twilit. When you make an attack with a twilit weapon to attack a target that is in dim light or darkness, you make the attack roll with advantage.
The biggest reason I find this to be a compelling read of the spell is that it has consistency with how other spells which conjure items, or creatures, behave.