- "I'm afraid it did not turn out as we expected..."
- —Igor, Persona 3
Fusion accidents are a hazard that can occur during demon fusion. This can either result in the loss of all component demons, or may result in something unexpected. Some races of demons can only be obtained via fusion accidents, often under specific circumstances. In many cases, Fusion accidents ignore level restrictions.
- Shin Megami Tensei II
- Shin Megami Tensei: if...
- Shin Megami Tensei III: Nocturne
- Shin Megami Tensei: Strange Journey
- Shin Megami Tensei IV
- Shin Megami Tensei IV Apocalypse
- Shin Megami Tensei: Devil Summoner
- Devil Summoner: Soul Hackers
- Devil Summoner: Raidou Kuzunoha vs. The Soulless Army
- Devil Summoner 2: Raidou Kuzunoha vs. King Abaddon
- Megami Ibunroku Persona
- Persona 3/FES/Portable
- Persona 4/Golden
- Persona Q: Shadow of the Labyrinth
- Persona 5
Shin Megami Tensei IIEdit
There is a rare chance that a fusion accident will happen, resulting in a different demon.
Shin Megami Tensei III: NocturneEdit
There is always a low chance of it happening with regular fusion; however, the odds of fusion accidents greatly increase in Full Kagutsuchi phases, though Special Fusions and Fiend Fusions are immune.
Shin Megami Tensei: Strange JourneyEdit
A fusion accident chances of happening increase with the Copernicus sub app, while Fracastoro prevents it. Using Copernicus with Zealot Summons increases the chances of getting a Zealot demon.
Shin Megami Tensei IVEdit
Generally, the chance of a fusion accident occurring is low (1/64), but fusing dead (0 HP) and/or Foul demons will increase the odds - each dead demon used increases the chance by 1/64, while including a Foul doubles the final chance, for a maximum chance of 6/64. When a fusion accident occurs, the result is typically within ~5 levels of what the normal result would have been, and the skill repertoire of the resultant demon is randomly selected from its default skills and its components' skills, except those of the Famed race, which are guaranteed to have their default skills. Most Famed race demons and Undead Corpse can only be created via fusion accident.
Shin Megami Tensei IV ApocalypseEdit
The mechanics for intentionally creating a fusion accident have been tweaked a bit since the previous game. In addition to using a 0 HP and Foul race demon to increase the chances, having Nanashi inflicted with the Sick ailment increases the base chance from 1/64 to 6/64, and each demon inflicted with the Sick ailment increases the chances by 3/64, allowing the player to increase their chances of an accident to the maximum by having Nanashi and two demons sick, one of which is Foul race, to 3/8 [(6/64 + 3/64 + 3/64) x2]. Once again, the majority of Famed race demons can only be created by fusion accidents, along with Undead Corpse and Zealot race demons.
If the player wishes to deal with the hassle, though Unique skills cannot normally be passed on through any type of fusion, with the except of a small select few through Fusion Lite, they can all be passed on via fusion accident.
Shin Megami Tensei: Devil SummonerEdit
Fusion accidents may occur while fusing at Hotel Gouma-Den at a low chance (1/256), which can be increased by fusing demons of the same race together with two of the same race resulting in a 1/32 chance and three resulting in a 1/16 chance.
Demons of the UMA and Enigma-races can only be obtained through fusion accidents, the former by using any of the Beasts family demons during a Full Moon and the latter by using any of the Gods family demons during a New Moon.
Devil Summoner: Raidou Kuzunoha vs. The Soulless ArmyEdit
A fusion accident in this game will result in one of five different types of Legion demon.
Devil Summoner 2: Raidou Kuzunoha vs. King AbaddonEdit
When fusion accidents occur it will become one of three demons: Fury Order Slime, Skill Order Blob, or Frost Order Black Ooze. If one attempts Fiend Fever or Evil Fever fusion and have all the demons of those orders on them, then one of the three slime demons will then be the result.
Megami Ibunroku PersonaEdit
Personas of the Fool Arcana can only be created through Fusion accidents. The other possible results are that the persona will be chosen at random from a different arcana, the persona will gain or lose stats, or will randomly inherit a skill from one of its "parents".
To guarantee a fusion accident resulting in a Fool Arcana persona, the player can take 101 or 230 steps from a "hard reset" (as in, not already mid-game and loading a save or selecting "Return to Title;" the player must exit the game to reset the) in an area where no enemies will attack, such as the Mikage Sun Mall (for an odd number of steps) or the Black Market (for an even number of steps), and performing a White Fusion, or by taking 275 or 546 steps and performing a Red Fusion. As the lowest level Fool is level 30, the protagonist must first be at least level 25.
A fusion accident resulting in +2 to all stats can be guaranteed by taking 6 or 25 steps and performing a White Fusion, and a random skill inheritance accident can be guaranteed by taking 31 or 62 steps with a White Fusion or 21 steps with a Red Fusion.
Note that, during the Snow Queen Quest, steps inside the infirmary count towards the number of steps for forcing a fusion accident. As such, it is possible to do any of the confirmed accidents since the player can take one or two steps prior to leaving the infirmary, allowing both even and odd step fusion accidents.
Also note that this works when using Totems and Gems, but not Skill Tablets or Items, so any extra skills wanted on the end result must be from inheritance. As Skill Inheritance functions as normal, it is likely that Unknown Powers do as well.