Can I throw dynamite from inside the effects of sanctuary?

Question

If not dynamite, then something similar like a bomb from the DMG.

Both have a similar rules text:

As an action, a creature can light a [stick of dynamite/bomb] and throw it at a point up to 60 feet away. Each creature within 5 feet of that point must make a DC 12 Dexterity saving throw, taking 3d6 [bludgeoning/fire] damage on a failed save [./, or half as much damage on a successful one.]

Nothing there says it targets/counts as an attack.

The spell Sanctuary says:

If the warded creature makes an attack, casts a spell that affects an enemy, or deals damage to another creature, this spell ends.

Do the rules consider you having dealt damage once the explosive goes off? Is it any different if you set the dynamite to explode after a set number of rounds (assuming you are still under the effects of sanctuary), and perhaps an innocent bystander walk by while you aren't looking?

Answer 1

Yes you can...

But the spell ends when you deal damage with the bomb.

Do the rules consider you having dealt damage once the explosive goes off?

The rules don't specify this explicitly. But allowing indirect damage begins a slippery path of extreme rules lawyering ("this wasn't me dealing damage, but my spear"). In some cases, RAW falls short. The writers are only human and can miss details. That's why we need a DM, after all. A bomb-throwing cleric under the effect of Sanctuary clearly goes against both the intention and the spirit of the spell.

Is it any different if you set the dynamite to explode after a set number of rounds

This is an edge case which needs DM's adjudication. I'd say it is still the character who deals damage. The character has agency, not the dynamite stick.

Answer 2

God knows what you did.

When sanctuary was originally published, it was available only to Clerics and Paladins. This gives some insight into the original intent for the spell's function. The question here is something like "Can I claim that it wasn't me, but it was the dynamite, that hurt those creatures?" And in the context of a caster deriving their power in some way from a higher power, as clerics and paladins do, you definitely cannot make that claim.

It seems clear enough that the last phrase, "or deals damage to another creature, this spell ends" is supposed to be the "junk-drawer" stipulation - it catches all the other junk that should end the spell that isn't technically a spell or an attack.

There is room for the DM to rule otherwise, but it seems pretty obvious that the "I didn't hurt those creatures, it was the bomb ^{_{(that I threw with the intent to kill those creatures)}}" loop hole is not how the spell is supposed to work.

Now, the spell sanctuary is available to the more recently published Artificer and the Genie Warlock, so I need to explain my argument a little bit more. There is no deity controlling the function or establishing the rules of an artificer's spells, so that is not the argument I am making for the artificer or genie-lock. Rather, I am saying "the spell originally functioned this way, for this reason, and did so for many years until the release of the artificer, which tells the intent for the spell's function. We then apply this intent for the spell's function to the newer use cases". But, it is because of the artificer and genie warlock having the spell that I say “there is room for the DM to rule otherwise”.