Morgenstern Revisited: Concussive Fireball & Deteriorate

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For our return to the Morgenstern Revisited posts, I present two more spells that were inspired by twisting their standard cousins in a new direction, concussive fireball and deteriorate, from Morgenstern’s Spellbook.

Fiery Boom

Concussive Fireball was Morgenstern’s attempt to cram even more damage into a 20-foot radius explosion. It was inspired by the line at the end of the first paragraph of the 3.5e fireball spell description, “The explosion creates almost no pressure.” The obvious question was, “what if it did create pressure?”

As with many of the spells in fifth edition, for fireball the devs dropped the xdy damage per caster level in favor of a fixed amount of damage, with higher-level casting benefits. While prepping to convert concussive fireball to 5e, I noticed the damage for the current fireball spell, 8d6, is about 25% more than the suggested damage for a 3rd level area of effect spell with a save, 6d6. I wondered if there was a typo, so I hit the internet. Nope. Apparently, it was a conscious decision because of the spell’s iconic nature. Cool.

My first thought was to scale the new concussive fireball damage proportionally by the ratio of the old concussive fireball maximum damage to the old fireball max: 16d6/10d6. That would mean a total of 12d6 damage (split over fire and thunder) for the new version. Even I can see that would be overpowered. So I’ve opted instead to keep the base 8d6 fire of the 5e fireball and just add 2d6 thunder damage, as befits a 5th level spell. But, unlike regular fireball, the higher-level casting benefit will be thunder based.

Concussive Fireball

5th-level evocation [sorcerer, wizard]

Casting Time: 1 action
Range: 150 feet
Components: V, S, M (a tiny ball of bat guano, sulfur, and bronze dust)
Duration: Instantaneous

At your gesture two tiny spheres of light streak toward a point you designate in a tightly spiraling double helix. Upon reaching the target location the spheres burst out in a fiery, thunderous explosion which spreads out in a 20′ radius sphere. The fire spreads around corners, igniting flammable materials as the thunder echoes from surrounding surfaces like a roll of thunder. Each creature caught in the 20′ burst must make a Dexterity saving throw and a Constitution saving throw. On a failed Dexterity save, the target takes 8d6 fire damage, or half that on a successful save. On a failed Constitution save, the target takes 2d6 thunder damage and is deafened for 1d4 rounds. On a successful Constitution save, the target takes only half the thunder damage and is not deafened.

At higher levels: When you cast this spell using a spell slot of 4th level or higher, add 1d6 thunder damage and 1d4 rounds of deafness per spell slot above 3rd.

A Touch of Destruction

Rasmus Morgenstern suffered from bouts of deep melancholy, and deteriorate was conceived on one of his darker, more destructive days. He reasoned that if we can magic away damage to an object with mending, we can damned well pile it on with magic, too. He would sometimes while away hours, with whiskey and pipe, while slowly destroying any little object within reach.

The original version of deteriorate was a 3rd level spell with a long duration, that slowly dealt damage to objects and constructs, one hit point at a time. With fifth edition, many massive objects and some merely large ones have damage thresholds below which damage is simply ignored. I thought about increasing the damage per round of deteriorate, but I wanted to keep the sense of slow decay. So, instead, I’ve decreased it to a cantrip, reduced the duration, and removed the vocal component. Because it’s always easier to destroy than create.


Transmutation cantrip [druid, warlock]

Casting Time: 1 action
Range: Touch
Components: S, M (a pinch of anhydrous acid)
Duration: Concentration, up to 1 minute

Deteriorate slowly wreaks rot and ruin on an object you touch, such as a rope, barrel, article of clothing, or other bit of gear. Small holes, tears, and cracks appear and grow on the object as it molders and disintegrates. After you touch the object upon casting the spell, it takes 1 hit point of damage each round for as long as you maintain concentration.

Have any Question or Comment?

2 comments on “Morgenstern Revisited: Concussive Fireball & Deteriorate

I like both of these! You might want to note that Deteriorate bypasses up to N points of that damage threshold (so that it could destroy, say, stone but not adamantium). Also, if Concussive Fireball includes a pressure wave, it might make sense to have it push people back from the center of the blast when they fail their Con save. Maybe just 5′, maybe casting-level-dependent?


Those are both interesting suggestions. I particularly like the thought of swapping out the deafness for a push, since being deaf is rarely problematic.

Later edit: Although, thinking about it, any concussive wave strong enough to push you back five feet is going to blow out your eardrums and then some. So, maybe we’ll stick with deafness. 🤣


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