Does a Javelin of Lightning allow a cleric to use Thunderous Strike?

Question

This question asks about ways for a Tempest cleric to use their Thunderous Strike class feature.

Thunderous strike says (emphasis mine):

Thunderous Strike. At 6th level, when you deal lightning damage to a Large or smaller creature, you can also push it up to 10 feet away from you.

One answer suggests various magic items, including a wand of lightning bolts and javelin of lightning.

The wand grants you the ability to cast a spell, and your spell means it is you doing the damage.

It is not as clear to me that this is the case with the javelin, however (emphasis mine):

When you hurl it and speak its Command Word, it transforms into a bolt of lightning, forming a line 5 feet wide that extends out from you to a target within 120 feet. Each creature in the line excluding you and the target must make a DC 13 Dexterity saving throw, taking 4d6 lightning damage on a failed save, and half as much damage on a successful one. The lightning bolt turns back into a javelin when it reaches the target. Make a ranged weapon attack against the target. On a hit, the target takes damage from the javelin plus 4d6 lightning damage.

By standard use of "you do damage", the weapon damage from the javelin itself is done by the person who throws it. But if the javelin is transforming itself to cause the lightning damage, is that damage still done by "you" (the thrower) in a way that would trigger Thunderous Strike, or is it rather done by the javelin, and independent of the thrower?

Related: What is damage you do vs. damage a creature takes?

Answer 1

To quote Naut Arch's answer

It's going to be up to the situation and up to the DM

There are no rules that specify who does what when it's not a directly related cause and effect that can easily be traced back to a creature. Heck, it's not even always cut and dry to trace back to a creature.

Because of that, the situations will matter and it will end up being a DM decision as to if the warlock is the source or something/someone else.

---

Personally, clearly the thrower of the Javelin is dealing damage

This specific case does not give any truly explicit indication of who/what is dealing the damage. That said, the weapon does state the following:

[...] Make a ranged weapon attack against the target. [...]

Where you, the attacker, the one using the Javelin, are making the attack. However, this is, technically, not 100% utterly and entirely explicitly stating that you are also the one dealing the damage. In fact, the same weapon later states (emphasis mine):

[...] the target takes damage from the javelin plus 4d6 lightning damage. [...]

I believe "from the Javelin" here is merely meant to convey that the target takes the regular damage as well as 4d6 lightning damage instead of just 4d6 damage, but this could still be construed as meaning the Javelin itself is dealing its normal damage and then also the 4d6 lightning damage.

The weapon's description is not perfectly clear, but I would rule, in a heartbeat, that the one using the Javelin is dealing damage with said Javelin and thus they are the one dealing the damage. Perhaps the Javelin is also dealing the damage (after all, damage need not be caused by only one thing), but until a scenario arises where that call is required, I do not know how I would rule. I almost can't imagine anybody even claiming the attacker isn't the one dealing damage because it would be like arguing somebody swinging a sword isn't dealing damage when they very much are.

---

What about the saving throw damage?

It is, of course, also ultimately up to the GM. That said, I would similarly, personally rule that this damage is also caused by the one attacking with the Javelin. They are the one who is dictating its path and choosing where the Javelin is sent, they have a great enough amount of agency in this scenario, they can, to me, meaningfully be said to be the causer or the damage, that I would conclude the damage can be considered to be being done by them as well.

Answer 2

The character throwing the lightning javelin is doing the damage.

tl;dr The thrower used their action to hurl the javelin and activate it is responsible for the damage.

Lacking a specific game definition of "who" and "does" we assume the vernacular meaning of "who does it?"

• The damage is a direct result of the action of the javelin thrower.
• The damage is a direct result of the attack roll of the thrower.

The damage is done by the thrower as it's their action, their equipment, and their attack.

Asserting the thrower doesn't do the lightning damage would strain most common interpretations of causality and culpability. Akin to "characters don't harm creatures, arrows and swords do."

The implement of the damage is the javelin, but isn't relevant for Thunderous Strike.

The javelin is the implement of damage. Similar to throwing an acid vial or alchemist's fire. It would be relevant if the class feature indicated the damage needed to be done with a weapon or spell, but in this case, any damage will do.