Who does the Hellish Rebuke spell target when the Warding Bond spell has been cast?

Question

The description of the warding bond spell says, in part (emphasis mine):

This spell wards a willing creature you touch and creates a mystic connection between you and the target until the spell ends. While the target is within 60 feet of you, it gains a +1 bonus to AC and saving throws, and it has resistance to all damage. Also, each time it takes damage, you take the same amount of damage.

The description of the hellish rebuke spell says:

You point your finger, and the creature that damaged you is momentarily surrounded by hellish flames. The creature must make a Dexterity saving throw. It takes 2d10 fire damage on a failed save, or half as much damage on a successful one.

When casting hellish rebuke, is the creature that receives the damage the one that cast warding bond? Or the one that attacked the creature that cast warding bond?

Both could be said to have damaged you, since the damage could not exist without both of them. Warding bond is the spell that actually gives you the damage, but it was cast before the damage was taken, and the attacking creature is the last one that creates a damaging action.

Answer 1

Ask the DM, but it ought to be the hostile attacking creature

The concept of the Warding Bond spell is that the two ring wearers are sharing the damage from a hostile third source. That's the spirit of the spell.

The language of Warding Bond says "you take" the same amount of damage (as the warded creature). That, to my mind, is not the same thing as the warded creature (or the warding creature) dealing damage. The damage was already on the table as a result of the original attack/spell. It just got divided up.

That's worth reemphasizing: the reason that the warding and warded creature both take damage is because some hostile creature attacked the warded creature with a weapon or spell. Without that initial damage, nothing happens.

I think it's possible make strict-reading arguments for either the warding creature or the warded creatures as being the source of the damage but the logic behind those arguments is not as compelling to me.

As is so often the case, the DM needs to decide how they want to arbitrate the event but, at my table, if the damage from a monster's attack is split between characters in this way, it's that monster that's going to get rebuked.

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Note that if both the warded and warding creature had access to the Hellish Rebuke spell, an available spell slot to cast it, and an unused reaction, they could both Rebuke the attacking creature.

I personally do not believe this is unbalanced but it is a consideration that the DM should keep in mind when deciding how to adjudicate the situation.

Answer 2

Hellish Rebuke does not have a valid target...

In this situation, the damage you take is done by Warding Bond. The spell states :

each time [the target of the spell] takes damage, you take the same amount of damage.

The spell description says "you take [...] damage", and does not specify any source for that damage. No matter if the damage is from a creature, fall damage, damage from a trap or anything of the sort, the spell will inflict damage on you equal to the damage taken by the target of the spell.

To put it simply, using your example : Alice takes damage from some damage source. The damage triggers Warding Bond, which inflicts the same amount of damage to Bob. Bob's spell inflicted this damage, not the original damage source that harmed Alice. Since the thing that harmed Alice did not harm you, you cannot target it with Hellish Rebuke.

... or does it?

The source of the damage you take through the spell is the spell you cast. So in theory, you are the creature that damaged you. That makes you a valid target for Hellish Rebuke, meaning you could point your finger at yourself and burst into flames.