HEY, IT WON'T LET ME FUSE THAT DEMON!

Learn why you can't fuse certain demons in Shin Megami Tensei III: Nocturne HD Remaster. Discover rules for bosses, mutation products, and Mythology fusions.

Even after following all the rules, you might still find yourself unable to fuse the demon you want. This can be due to several specific caveats within demon fusion:

1) Bosses must be killed before you can fuse them. If a boss is still alive, you cannot fuse it. The only exception is for bosses fought only on certain alignment paths; in these cases, you just need to pass the story point where you would have fought them. For example, the Daitenshi is not fought on the Yosuga alignment route. Once you progress past the point where you would have encountered them on another route, they become available for fusion. Note that a few bosses can be fused before you fight them, and one boss must be fought twice before fusion is possible.

2) Demons that are "mutation products" cannot be fused. If you attempt to rank-up Yama Nyx with a Seirei fusion, you won't get Yama Lilith because Lilith can be obtained by mutating Yama Lilim. Since Lilith is the highest-ranked Yama, you wouldn't be able to perform a rank-up Seirei fusion with Nyx at all. To obtain Yama Lilith, you must either mutate Lilim or recruit one directly through negotiation.

3) Demons fused via Mythology fusions can ONLY be fused through Mythology fusions. Therefore, attempting a rank-down Majin fusion with a Seirei fusion to get Majin Amaterasu won't work, as she has a Mythology fusion associated with her. Instead, you would get Majin Atavaka, the next highest-ranked Majin after Amaterasu.

Sacrifice Fusions

Sacrifice Fusions are a new addition to the Shin Megami Tensei series. You cannot perform them until you reach Ginza, and even then, only during a full Kagutsuchi. A Sacrifice Fusion is similar to a normal fusion, where you select two demons to fuse, but you also choose a third demon to "sacrifice." This functions like fusing three demons together, but operates differently than triple fusions in previous SMT games.

With the exception of Mythology fusions, sacrificing a third demon will not alter the resulting demon. For instance, if the first two demons would normally result in Kishin Zochoten, sacrificing any demon will still yield Kishin Zochoten. The benefit of Sacrifice Fusions lies in using the sacrifice to power up your target demon.

Normally, a target demon inherits skills only from its "parents." In a Sacrifice Fusion, the resulting demon inherits skills from all three "parents" and also gains any experience points the sacrificed demon has accumulated. The product of a Sacrifice Fusion receives one and a half times the experience points the sacrificed demon had. For example, if a sacrifice had 100 EXP, the fused demon gains an additional 150 EXP on top of its base state.

This allows you to obtain a leveled-up demon immediately upon fusion, without needing to train it from scratch. Its HP, MP, and stats will increase based on the levels gained through the fusion. However, there are caveats:

• The product demon, even with added EXP, cannot exceed the Hero's level. If the Hero is level 49, you can fuse LV47 Majin Atavaka. But if a sacrifice would raise Atavaka's level to 50, the fusion will fail because he would be too powerful.
• Demons will not learn skills they would normally acquire through levels gained via Sacrifice Fusions. They will learn these skills upon their next level-up. For example, Kishin Takeminakata has a base level of 17. If you fuse a Level 20 Takeminakata via Sacrifice Fusion, he won't initially have skills like Makajama, Threaten, and Parala-eye, which he would normally learn by battle. However, upon leveling him to 21, he will learn all those skills at once, plus De-Kaja (a skill normally learned four levels later).

Overall, Sacrifice Fusions are more beneficial than normal fusions, and you'll likely use them for almost all your fusions after gaining access. They allow you to retain the hard-earned experience of your party. However, the 1.5x experience bonus can become problematic. While you can repeatedly sacrifice developed demons, the experience bonuses can escalate, eventually causing your sacrificed demons to level up fusions by 10 or more levels. This renders them ineffective for creating demons close to your own level, unless your goal is to significantly boost a low-level demon.

Fusion Accidents

Fusion Accidents return from earlier SMT games and are more detrimental now. Unlike in Devil Summoner and Soul Hackers, where they could yield unique or powerful demons, they are now almost exclusively negative. Every demon fusion carries a chance of failure, resulting in an unintended demon.