Critical Ecstasy is a specific term used in the game, describing the heavily weakened state of a man when forced to ejaculate by a monster. Whenever he orgasms, although he feels pleasured, he suddenly becomes frail and loses the ability to fight back against the monster.
The term is stated by a Knight within Ilias Village, describing that ejaculation drains one's fighting spirit, according to scholars. In other words, if a man comes, his mind and spirit surrenders, and the monster will be able to have their way with him.
No matter the difference between the level of man and monster, the man will surrender if Critical Ecstasy is reached. For example, a level 3 Imp can have her way with a level 59 Luka if she can make him come.
Although not explicitly mentioned about its effects on monsters, Critical Ecstasy does not seem to weaken them, but still provides them satisfaction. Vampire Girl and Spider Princess orgasms during their rape scenes but remains in control of the rape with no signs of weakening; and Siren looks forward to her orgasm (which never happens). However, Granberia seems to be susceptible to pleasure, although this may be due to her inexperience with sex.
It is unknown if human women are vulnerable to Critical Ecstasy.