Monsterization

In the Monster Girl Encyclopedia world, monster girls are made as well as born. Monsterization is the umbrella term for a whole host of different processes by which men, women, corpses, plants, animals, elements, gods and various inanimate objects are all transformed into cum-guzzling nymphomaniacs.

A whole section of Fallen Maidens is devoted to case studies of different monsterization classes; see there for in-depth case studies on yuri, Demon Realm mana corruption, roper/slime-carrier/matango parasitism, dark slime melting, necromancy, the hand of god, snake pits, cursed items, alpification, and not eating properly.

The generic case

 * Refer to: Monsterization, MGE-1 and Monsterization Handbook, Fallen Maidens

Most people who get monsterized don't want to be monsterized, because the vast majority of people who undergo the process are female Order humans, and the Order teaches that anything that happens in relation to monsters is bad apart from zealous religious persecution. There are exceptions, of course; sorceresses may pursue witchdom or lichdom in their quest for magical power, and there are some heretical sects which hold monsterization in a positive light. Still, in the vast majority of cases, monsterization is a process violently resisted by those subjected to it. On becoming a monster, the fear and loathing a woman felt towards her own transformation does not necessarily melt away immediately. Elves and valkyries are notoriously conflicted about acting on their new irresistible impulses, and in Baphomet Complex, Lilia Flimlight's misgivings persist for hours even after she sleeps. But regardless of whether they're happy about it or not, their newly ravishing body is gripped by a throbbing, needy lust for male company. "Women who’ve only just become monsters still have their human values, but with the monstrous body that’s hot for men, and the intense feeling of hunger, the human mind can’t hold out. Driven by desire, they end up attacking human men ". It's at this point that those who had someone they truly loved as a human make a beeline towards their "husband"; for those who didn't, the first man they spot is likely to be attacked for their first semen meal.

The physical changes of rockin' tits, flawless sensitive skin, and more importantly, thirty foot tails or an ass the size of a wagon, therefore do not prevent the immediate use of those attributes for sexy times. It is not clear to how many of the monsterization methods or monster girl species this applies, but the succubus family at least tends to have their transformations go via a two-step process. First, the spirit energy is replaced with demonic energy, producing a partially-transformed lesser succubus. These creatures have protective fur over parts of their bodies, as lesser succubi have a monster's sensitivity but haven't yet acquired the monster's tolerance to supercharged pleasure; being groped too vigorously during semi-transformed sex is a sure-fire way to make them ahegao themselves unconscious. Lesser succubi must then rape their way to enough spirit energy to complete the transformation, and become a fully-fledged succubus.

The metaphysical aspect
To the casual bystander, monsterization usually involves a woman becoming substantially more attractive and then raping that bystander. But from a magical standpoint, all the significant stuff happens invisibly. The fundamental difference between being a monster and not being a monster is that monsters have demonic energy inside them and non-monsters don't. If a female is exposed to enough demonic energy, it snuffs out her ability to produce spirit energy; and the point at which this ability is destroyed is the point at which there is no chance of recovery. With only demonic energy left inside her, and no way to replenish her mana autonomously, milking men's semen for spirit energy is from then on her #1 source of magical sustenance. The reason that men can't be transformed into monster girls by this very same process is that men's autonomous spirit energy generation is much faster, and gets faster still in the presence of demonic energy, so it can't be snuffed out except in very peculiar circumstances. Or by death, after which point demonic energy could do unspeakable things to your bones.

Former humans who are transformed by sex tend to form a special bond of respect with the monster that transformed them. Both Lilia Flimlight and Wilmarina Noscrim come to view their lilim rapist as a second mother, and go on to work for them as subordinates. Those who have been transformed also tend to be more keen to transform others, as they know first-hand the thrill of monsters' sexual "liberation".

Historical relevance
The first and largest instance of "transformation into a monster girl" was the one that enraged the Chief God and produced the Monster Girl Encyclopedia world we know today. It was the great magical work that turned the skull-crushing, blood-drinking monsters of the former Demon Lord into the pelvis-groping, semen-drinking monster girls of the current Demon Lord.

So this wasn't so much a "monsterization" as a "succubusization", from one kind of monster to a different, hybrid kind. Just as humans who are transformed into monsters rapidly begin to prefer their new forms for all the mind-shaking pleasure it brings, the monsters transformed into monster girls all seem to like it this way too (though the ones in Zipangu don't like it quite enough to contribute to the Demon Army ). Exactly what happened to the formerly male members of the monster species is not known.

Early in the current Demon Lord's reign, the depraved dark elves appealed to the succubi for super-hedonistic bodies too, and that race quickly became entirely monster. The dwarves went the same way, albeit somewhat slower and with less intentional planning. The Fairy Kingdom races are on the path to monsterization after the Sabbath decided to aggressively proselytize amongst them. In the current era, transformation into a monster girl is mostly accomplished by the various one-on-one methods mentioned previously: getting yuri raped by a succubus, having a parasite egg stuffed up your barren vagina, being mauled by a werewolf, etc. Although it isn't stated outright, it doesn't seem like any non-monsters could be converted into monsters before the current era; otherwise, the dark elves (and dwarves) could have asked the succubi to turn their women into sexy sluts in any of the previous ages.