[RPG] Is it possible create Megumin in D&D

character-creationdnd-5e

Recently I watched an anime called Konosuba and I loved the archmage style. She can only cast the Explosion spell and only once a day because it drains all her mana and after casting the spell she can’t move for a while. Is it possible to create Megumin in this game if so how do I do it?

For context Megumin as a character knows only the Explosion spell (which is essentially just a massively explosive fireball) and refuses to learn any other form of magic. Casting that spell takes all of her energy or mana and leaves her completely unable to move for a while and even after, she is unable to cast it again for the remainder of the day (barring special circumstances in the anime).

Best Answer

You can't really do this in D&D 5e (but could in AD&D).

In D&D terms, Megumin is an arcane spellcaster who can only cast one exceptionally powerful spell per day, which consumes all of her power.

However, none of the core classes in D&D 5th edition can do this, exactly. The mechanics of arcane spellcasting use spell slots, so that it's not possible to spend all your MP on a single strike. The generally well-balanced nature of D&D 5e, and limit on the number of first-party splatbooks compared to earlier editions, limits the ability of player characters to channel all their offensive power into a single attack.

However, we can build something akin to Megumin.

Approximate equivalent to Megumin in D&D 5e

Sorcerers in D&D 5e gain sorcery points, and their Flexible Casting ability allows them to convert spell slots into sorcery points. You could, in theory, convert all your spell slots to sorcery points, given several rounds of preparation. This would meet two requirements of a Megumin build:

  • Can only cast one spell per day
  • Takes a long time in preparation to cast this spell

Metamagic allows the sorcerer to spend sorcery points to empower their spells. A level 6 character—canonically Megumin's character level at the beginning of the series, assuming equality with D&D's levels, which is not unreasonable since the goddess Aqua is level 21—could accumulate 22 sorcery points this way by spending 9 bonus actions, or one minute.

You can therefore apply both Empowered and Heightened Spell to a fireball, giving you a reroll on damage dice and giving one target disadvantage on the saving throw, for a total cost of 4 sorcery points.

  • This meets the requirement of one very powerful fire spell per day.

However, you can only spend 4 sorcery points this way. This means that you have enough sorcery points and spell slots to cast these empowered heightened fireball three times per day, rather than Megumin's one per day. The limit is that there's no way to channel all this power into a single spell per day.

At sorcerer levels 7, 9, and 11-20, you will only have one spell per day of your highest level spell. However, you can't sacrifice all your low level spells to empower it, as the limit on spending sorcery points still applies.

That said, it's canonically the case that Megumin actively refuses to learn any spell except Explosion, so it's possible that she merely has one powerful spell of her highest level and simply refuses to learn any spells in her lower-level slots. In that sense, a valid representation of Megumin is merely one who casts a single empowered spell; though, again you can't actually sacrifice all your low-level slots to further empower it.

You also can't really have the character faint from exhaustion. There are exhaustion rules, but there are no official rules by which spellcasting would exhaust you.

However, you could do this in AD&D 2nd edition

A quick search reveals an article titled D&D's influence on Konosuba, which posits that in AD&D 2nd edition it was indeed possible to play a Megumin character using the custom character class rules in a certain sourcebook:

AD&D 2nd edition expansion Player’s Option: Spells & Magic actually made it possible to construct a custom wizard class that only knows one specific type of magic, has trouble learning new spells, can only cast one extremely powerful spell per day, has to chant dramatically to cast it, and collapses at the end.

The cover of that same book features a wizard attacking a castle with a massive fireball.

The spell points and custom character class creation rules in Player’s Option: Spells & Magic allow you to create an actual hyper-focused level 6 character who can functionally channel all their "MP" into a single, extremely powerful home-made signature spell once per day, but will faint thereafter.