Final Fantasy XIV has you covered. The nuke-equivalent is
primals, also known as "eikons," "eidolons," "kami," or "summoned deities." But "primal" is the most common term used in-game, so I'm sticking with that.
Avoiding spoilers (because
boy howdy are there a ton on this subject), a primal is a being created through a ritual which consumes a very large quantity of aether (the raw material of magic, souls, life, etc.) As part of the ritual, the people performing it express their fervent devotion to whatever deity they value most, e.g. the first primal the player character faces is Ifrit, the fiery semi-reptilian deity of the Amalj'aa. This devotion, through the ritual, transforms the provided aether into a magical construct that retains the full force of all the energy put into it, and is capable of incredible feats of magic and destruction (or creation, for the few that actually care about that.)
Unfortunately, there are three extremely serious problems with the creation of a primal. They are, in no particular order:
- Because primals are created by fervent worship, they are born with an intense desire to force other beings to follow them as well--they are jealous gods. This makes them extremely aggressive and dangerous (hence why most are destructive rather than constructive.) In most cases, primals are summoned by desperate groups looking for salvation from their troubles, so the destruction generally has a salvific/righting-wrongs edge to it that makes the situation even more difficult.
- Due to the specific nature of the summoning ritual...the being created can mind control (usually called "Tempering") anyone nearby. Only a very few people are immune to this effect, the player character being one of them. You literally only need to be physically close to the primal and they can temper you, making you (at absolute best) a fanatically devoted worshiper, and at worst zombie-like or even catatonic. No one has ever found a cure for tempering, and tempered people cannot be allowed to live, as their very existence empowers and sustains the primal, which is bad because...
- Primals innately drain the aether of the land around them. They are, in effect, an unstable magical reaction slowly "burning up" the aether they're made of. If they don't get new sources of it, they'll die--so they constantly absorb aether from the land and even from people. If a primal is allowed to run amok for an extended period of time, an entire region could be sucked dry of aether, leaving a barren wasteland, devoid of life. (All life in FFXIV requires a steady flow of aether in and out--if the aether is removed or ceases flowing, life simply ends.)
It's got all the "fallout destroys the land" of actual nuclear weapons,
plus the fact that literally the only thing you need is ritual knowledge, a truckload of aether (usually in the form of crystals, which are basically solidified aether), and fervent belief. And then you add on top of it the horrifying effects of tempering and how that makes primals not only self-sustaining but with an active regeneration source (tempered people don't
stop being tempered when the primal is destroyed; they'll actively do everything in their power to restore their primal overlord.) For the rotten cherry on top of this garbage sundae, as noted, the people most likely to summon primals are those who have already been abused, hunted, coerced, pushed into a corner, or faced with extinction (whether by happenstance or by extermination), so it's not even like these people
don't have a reason, they absolutely DO, they're just turning to the WORST possible tool they could because they believe they don't have any other options.
And finally, as the sauce atop this garbage sundae? There's a cult of weird immortal jerks, the Ascians, who are responsible for making sure that every disenfranchised group the world over knows
exactly how to perform these summonings, and even how to power them up with
ritual sacrifice of other people.
Primals. They're the perfect magical nuclear weapon analogue.