I'm interested in hearing this actually, although I'm guessing this involves Order of Scribes and Wildfire Druid in some capacity.
Bingo (and good morning, all)!
Dragon sorc (fire) 6/Wildfire druid 6/Scribe wizard 2/Fighter 2/Hexblade warlock 1
Order of operations:
Summon wildfire spirit. Here's where we need that extra action for setup, but as mentioned the spirit lasts for an hour at a time, doesn't take concentration and is capable of movement (flying movement at that). 1 action
Then we use the utterly stupid Hexblade's curse on the target. No roll involved here either. 1 bonus action
We cast Magic Missile using our 9th-level slot, and use our scribe book to change its damage type to fire (requiring us to have recorded Meteor Swarm or similar in the book, which is technically fine according to the rules since we don't need to be able to have exclusively
wizard levels for the spell slots of spells we write down in our wizardly book). At 9th level, MM provides 11 missiles. 1 action
Action surge. No action
Using our surged action, we cast Magic Missile again using our next highest slot which is 8th level. 10 more missiles. 1 action
At Wildfire druid level 6, while our wildifire spirit is active we can add +1d8 to one roll of either fire damage or healing amount when casting an appropriate spell (one that heals or does fire damage, namely). The damage of every magic missile is calculated using one roll, according to Crawford, so it applies to the damage of each individual bolt.
Dragon sorc 6 gives a bonus equal to your Charisma modifier to one damage roll of a spell you cast that uses your attuned element. Again, one roll, so the modifier gets applied to every missile (and we can have 20 CHA here, because you don't technically need any more than 13 Wis or Int as far as either the druid or wizard are concerned). That's a +5 damage bonus, per each missile.
Order of scribes 2 gets us our fancy book, which lets us change the damage type of a spell on the fly so long as we have an example of that damage type at the spell level we're casting the spell at. So we need to have scribed 8th and 9th level spells with fire damage in order to get this to work, but beyond that we don't need to cast them and modifying a spell this way doesn't take any other sort of resources. Note that while the description does say that you can only do this when casting
wizard spells, that doesn't actually mean anything important for us because we
are casting MM as a wizard spell! Our INT doesn't matter in this case, because there are no attack rolls or save DC.
Fighter level 2 is obvious, action surge 4 lyfe.
Hexblade 1 is of course the 1-hit wonder that gives us the utterly stupid Hexblade's curse, a bonus action no-save no-concentration hex where "You gain a bonus to damage rolls against the cursed target. The bonus equals your proficiency bonus." There's that damage roll again! And at level 17, we've got a proficiency bonus of +6.
So the damage per missile is 1d4+1(base spell), +1d8(wildfire spirit bonus), +5(dragon sorcerer), +6(Hexblade's curse). And using up a 9th and an 8th level slot for casting MM, we end up with a total of 21 missiles.
Resulting in 1d4+1d8+12 x21 (okay, so it's x11 + x10 since you'll be rolling the d4 and d8 again, so sue me) fire damage with no save and no attack roll.
It's significantly weakened against fire immune monsters, as you'll have to use a different damage type and won't get either the +1d8 or the +5 bonuses in that case. ...and of course the entire thing is instantly and completely blocked by simply reacting with a casting of Shield, but meh
Finally, something that can compete with the damage potential of Paladins! And at only level 17!