During the last game I mastered, my party looted a Ring of Spell Storing. With that object came a lot of questions most I could answer, some I was not exactly sure what to say and they were mostly revolving around Hellish Rebuke.
The first thing I was not certain how to answer was: is it possible to cast a reaction spell with strict conditions of casting such as Hellish Rebuke into the ring ?
If it is possible does the original caster of the spell have to take damage (for the example of Hellish Rebuke) to be able to cast the spell into the ring or does it only apply to the character using the ring to cast (or both)? And for any other spell does the casting time has to be respected when the spell goes into the ring, out of the ring or both?
Best Answer
Short Answer: Hellish Rebuke can be stored into the ring, but the caster has to be first harmed to store it, and it will only have an effect if the ring bearer is harmed by an attacker when it is used from that ring.
So this is an interesting question. Now on the basics of the ring, a Ring of Spell Storing can store any spell of levels 1 through 5. Casting the spell uses all of the properties of the spellcaster that stored the spell, but otherwise it is activated by the spellcaster.
What is different is that according to Hellish Rebuke, it is only activated as a reaction, and a reaction to being dealt damage by a creature. So it seems that to even cast the spell to begin storing it, the caster would have to be attacked and harmed by someone. The spell can still be stored into the ring instead of the attacker, the only restriction to this spell is what triggers it.
Now when the spell is in the ring, and the ring bearer wishes to activate it, they can only do so if they are damaged by an attacker. The spell still uses the spell save DC, spell Attack bonus, and spellcasting ability of the original caster, but it is the ring bearer that casts it in reaction to the damage, and designates the target (in the case of multiple attackers in the turn).
And now cue funny stories of party members finding creative ways to deal minimal damage to a Warlock to store the Hellish Rebuke into the ring for someone to use. Vicious Mockery is a personal favorite.