Do spells/abilities that do extra damage on a weapon attack apply to the damage of Steel Wind Strike?

Question

The Steel Wind Strike spell description (Xanathar's Guide to Everything, p. 166) says:

You flourish the weapon used in the casting and then vanish to strike like the wind. Choose up to five creatures you can see within range. Make a melee spell attack against each target. On a hit, a target takes 6d10 force damage.

The particularity of that spell is that, contrary to many other weapon damage-based spells and abilities, this one doesn't add 6d10 on top of your regular damage output, it just does 6d10, which leads me to assume that it replaces your normal damage (for example, a greatsword used for Steel Wind Strike wouldn't do 2d6+Strength slashing damage, it would just do 6d10 force damage).

Do other spells and abilities that add damage to weapon attacks (such as the ones in this nearly exhaustive list) work on top of Steel Wind Strike (for at least its first successful attack)?

Answer 1

Melee Spell Attack

Steel Wind Strike (Xanathar's, 166) requires you to

Make a melee spell attack against each target

This is not a Melee Weapon Attack so many, if not all, of the listed options are not relevant.

However, any feature that lets you add additional damage on top of a Melee Spell Attack would still be viable.

Answer 2

No, because it's not a weapon attack

The steel wind strike spell basically ignores the weapon you're using to cast it, from a mechanical perspective - you simply make melee spell attacks against up to 5 creatures within range, and do 6d10 force damage to each one you hit.

The material component of the spell is listed as:

(a melee weapon worth at least 1 sp)

The cost requirement is simply to ensure that you can't substitute a component pouch or spellcasting focus for the material component of the spell. Aside from that, the properties of that weapon are totally irrelevant.

You might be able to apply any features that are triggered by "an attack" or "a melee attack", but none that are triggered by "a weapon attack". The "spell attack" and "weapon attack" categories are mutually exclusive.

Answer 3

Abilities that trigger from melee weapon attacks don't work. Abilities that trigger from attacks that use melee weapons do.

In short, Steel Wind Strike uses a melee weapon to perform a melee spell attack. This means that while it doesn't work with abilities that require melee weapon attacks, it does work with abilities that simply require am attack with a melee weapon. For instance, it will work with a Rogue's Sneak Attack, since that merely requires an attack using a melee weapon with the Finesse tag.