Although not present in all of its games, the Shin Megami Tensei series typically contains a merchant-type service in each game with which you can sacrifice two or more of the creatures following you at that moment in order to create a significantly more powerful entity to help you. These new monsters often have techniques and defenses that will help you to stay a step ahead of, or at least to keep up with, the game's challenges, which is important in an SMT game, let me tell you. Besides the fact that it opens up options for party-member creatures that probably can't be recruited just yet otherwise, Demon Fusion is also handy in that the demons you make will often have slightly boosted stats over what the same monster would have if you just recruited it in combat (or, in the SMT Persona games, get an experience boost that may raise its level), may have some kind of bonus item to give you, and will inherit some of the skills of the monsters you sacrifice for it.
This latter component, however, is the reason that I FUCKING HATE DEMON FUSION WITH ALL THE BITTER, BLACKENED LUMP OF ANIMOSITY THAT IS MY SOUL. You see, it's like this. Before each Fusion actually occurs, you get to see a preview of the monster that will be created. You can see which creature it is, the stats, and the skills, both the inherent ones and the one's it's getting from its parents of sorts. The inherited skills are mostly randomized--unless there's a skill in the parents' set that can't be used by this type of creature, or a skill that can ONLY be used by that sacrificed creature, then any and all of the predecessors' skills are up for grabs via random selection. If you don't see the skill(s) you want, you just nix the Fusion, then try it again.
And again. And again and again and again...simulating this process in text will be boring, so let us instead say: (And Again) x N, where N = any positive whole number less than or equal to 500.
It's not so terrible in the beginning. In the early stages of the games, the monsters you fuse don't have all that many really noteworthy skills to pass on (in fact, they don't even have that many skills, period, so there's less for the random process to choose from), so the most you'll probably want is for the new monster to have one or two varied elemental attack spells. That's not a real problem; you might even get an acceptable spell for the new creature on your first try. It'll surely take you no more than 10 attempts. No problem.
It's later in the games where this process becomes more annoying than the stupidest minigame you've ever played. You'll be sacrificing 2 or more creatures that each have probably 5 - 8 different skills for the inheriting process to randomly choose from, and you'll almost certainly have at least 2 you'll adamantly want your new beast to inherit. I think that the best way to properly describe exactly what makes this whole thing horrible is to run through how it usually goes for me.
BEGINNING: "Oooh! Look at that awesome demonI can create! It's got great resistances, and its only weakness is Fire...but one of the monsters I'm sacrificing has Null Fire, so that'll fix that and make it an ideal front-lines tank! Let's see...I'd also like to see Sacrificial Monster 1's all-healing spell and Resist Physical skills on the new one, and Monster 2's got the same all-healing spell and the ultimate Wind spell, which would be handy. The new monster's going to inherit 3 skills. I know I HAVE to have Null Fire, and I'll be happy with any combination of the other 3 skills I like for the others."
AFTER SETTING THE FUSION UP, SEEING WHAT WILL RESULT, CANCELING IT, AND TRYING AGAIN 50 TIMES: "Okay, this is getting tedious. Damn that randomizer! Fine, I won't be greedy. I'll just insist on having Null Fire and 1 of the other 3 skills I wanted. But of them, Resist Physical and the Wind spell are better, so it'll have to be 1 of them; I'll just give up on the healing spell. And whatever the last slot's filled with will just have to work for me."
AFTER 50 MORE TRIES: "Oh my GOD, how is it possible that random chance wouldn't EVER give me a skill combination I want? Fuck it, I am NOT compromising on this; I want Null Fire AND Resist Physical or the Wind spell. Sooner or later it has got to happen."
AFTER 75 MORE TRIES: "N...No...gotta...gotta stay strong...no compromises...it's gotta happen some time..."
AFTER 50 MORE TRIES: "FINE! I'll accept the healing spell for the second must-have skill. Just so long as Null Fire's with it. That betters my chances for something acceptable, right?"
AFTER 75 MORE TRIES: "Oh Jesus I give up. Just Null Fire. I'll just give up on anything else I want. Just the one damn skill. Anything to get on with things."
AFTER 50 MORE TRIES: "GRRAAAGGHH! Why won't Null Fire even come UP any more? Can this game HEAR me?"
And finally, after a few more tries during which I am screaming, slamming my fist down on my desk, and generally carrying on, I'll get a Fusion possibility that has the Null Fire in it, and I'll tearfully just accept this meager, disappointing offering, now a broken and disturbed man.
What is the POINT of this idiocy? What are they THINKING by randomizing the thing? By letting the gamer know what skills are inherited ahead of time, the SMT makers are basically encouraging the gamer to set the Fusion up over and over again to get at least SOME skill they want, so if the intention of randomizing it is to leave whether you get good skills or not entirely up to chance, the makers have failed, because the gamer has the opportunity to make sure that at least some of the skills they want are certain to be there. Why not just make a Demon Fusion process where you pick and choose a skill or two that you want to keep? I don't even care if they'd have to lessen the number of inherited skills possible down to just 1 or 2; that's really all the preferred skills I'm ever getting anyway, and it'd still save me all the time it takes to get them otherwise.
And yeah, you can try to say that it could be worse, that the creators could just not show you anything ahead of time and let you get whatever skills the game decides AFTER the Fusion, when it's too late to change anything, but I actually think that would STILL be less annoying. At least in that circumstance, you're limited by your money and monsters in the game as to how many times you can redo the Demon Fusion to get the abilities you want out of it. You would have to just accept it and move on; you wouldn't have the choice of setting up and canceling out of the Fusion 1000 times to get it just like you want it. Sure, it would still be a pain in the ass and make things more difficult...but it wouldn't be so aggravatingly monotonous. How can these games be created with such attentive care to detail in all the other aspects of game play, but keep recycling this poorly-conceived nightmare over and over?