I kept finding homebrew rules for adding sex to Pathfinder that focused on all the extra details you could add. My biggest gripe with those sources being that they almost never defined the core mechanics of the interactions. I was also disappointed with rakevuril's rules for adding vore to Pathfinder. So I stripped out all the feats, magic items, spells, etc and tried to boil down the rules into the most simple of concepts.<br/><br/>For sex in d20, I tried to focus on just what the basic sex check should be, how long sex can last, and pregnancy chance and duration. For vore, I focused on the act of swallowing, digesting, and reforming prey. All rules assume Humanoid creatures using them, but may be modified as seen fit.<br/><br/>None of this is perfect, and you are free to ignore it if your wish, but these are just my, admittedly, barebones ideas of how to utilize these acts without having to read through an entire PDF to understand them.<br/><br/><span style="font-weight: bold"><span style="text-decoration: underline"><span style="font-size: 150%; line-height: 116%;">SEX RULES FOR PATHFINDER</span></span></span><br/><br/>A character has to make a level-based check to please their partner. Use the following formula for this: 1d20 + 1/2 the character's level + the character's Charisma modifier.<br/>Spells, Feats, Magic Items and other modifiers may be allowed by the GM.<br/>DC is equal to 10 + 1/2 Target's HD.<br/>There is a +2 Modifier if the target is Fey, Monstrous Humanoid, or Outsider.<br/>There is a +5 Modifier if the target is Animal, Dragon, or Magical Beast.<br/>There is a +10 Modifier for all other creature types (expect Humanoid).<br/>There is an additional +4 Modifier for each size category of difference between target and character.<br/>Certain types of sex acts may add or subtract difficulty at the GM's option.<br/><br/>Sex lasts a number of rounds equal to the lowest Constitution score among participants.<br/>All parties are fatigued after sex, though they may go again, taking non-lethal damage each attempt equal to 1d4 x the number of engagements prior.<br/>If a character takes enough non-lethal damage to be knocked unconscious this way, they may not have sex for a week as their body needs to recover.<br/><br/>Size difference can also cause pain or injury. A female character engaging in penetrative sex with a partner of a larger size category must make a Fortitude saving throw or suffer the male's Hit Dice in bludgeoning damage.<br/>The Fortitude DC is 15 + Size modifier for each size category beyond the first + the male's Strength modifier.<br/><br/>Pregnancy chance is based on each race's Adulthood age.<br/>Pregnancy Chance = 100 - Adulthood age. (Elves and other races with Adulthoods after 100 years take the remaining absolute value as their pregnancy chance.)<br/>Core Races: Human 85%, Dwarf 60%, Elf 10%, Gnome 60%, Half-Elf 80%, Half-Orc 86%, Halfling 80%<br/>Constitution also plays a role in conception rate. Characters with high constitution add each point above 10 to their base pregnancy chance. Characters with low Constitution scores subtract each point below 10 from their pregnancy chance.<br/>Crossbreeding: Between Humanoid species, take the lower percentage and divide it by half. These rules don't go into specifics on crossbreeding with demons, dragons, etc.<br/>The base pregnancy chance should be used if both partners are trying to conceive. If one or both parties are not actively trying to conceive, divide the pregnancy chance by half (this is on top of the crossbreeding penalty).<br/>At the GM's option, certain spells, such as Bless or Bestow Curse can further increase or decrease conception rates.<br/><br/>Pregnancy length is based on each race's average Maximum age.<br/>Pregnancy length = Racial average Maximum age / 10 in months, rounded down.<br/>Core Races: Human 9 months, Dwarf 35 months, Elf 55 months, Gnome 35 months, Half-Elf 15 months, Half-Orc 7 months, Halfling 15 months<br/>Penalties for being pregnant. During the First Trimester characters are treated as if carrying a light load, during the Second Trimester they are treated as if carrying a Medium load, and during the Third Trimester they are treated as if carrying a heavy load.<br/>Crossbreeding: The duration of a pregnancy between different races is the average of both. Example: A pregnancy between a Human and an Elf is (9 + 55) / 2 = 32 months. The resulting child is usually of the mother's race, with some physical traits picked up from the father's race. The exceptions to this rule are as follows: Crossbreeding between a Human and Elf results in a Half-Elf, Crossbreeding between a Human and an Orc results in a Half-Orc. Half-Elves and Half-Orcs crossbreeding with either of their parent races produce Half-Elves and Half-Orcs as well. Crossbreeding between a Half-Elf and a Half-Orc has a 50% chance of resulting in the mother's race or producing a Human.<br/>Complications: Damage, disease, and harmful magic can all cause complications during birth. A general rule to apply is that if the character must make a Fortitude save against a harmful effect, failure also causes a miscarriage.<br/><br/><span style="font-weight: bold"><span style="text-decoration: underline"><span style="font-size: 150%; line-height: 116%;">VORE RULES FOR PATHFINDER</span></span></span><br/><br/>Tug of War<br/>Swallowing Prey is a long process. During that time, the Predator must hold their breath to do so (if swallowing Orally).<br/>When swallowing Prey, track how many times the Predator has succeeded versus the Prey's Strength or Dexterity score (whichever is higher).<br/>A Predator has fully consumed their Prey when the number of successes they've made matches the Prey's Strength or Dexterity score, a Prey has escaped if they manage to bring the Predator's net successes to zero.<br/>If a Predator starts taking damage from suffocation, they immediately expel their prey and are unable to make another Swallow attempt for an hour.<br/>Prey may relent to the Predator, allowing the Predator to consume them in half the given time. This also grants the Predator automatic successes for their Swallow checks.<br/>Smaller or Larger Prey Halve or Double, respectively, the Swallow time for each Size Category of difference between Predator and Prey.<br/><br/>Digestion<br/>NOTE: The predator is under no obligation to digest their prey, and may hold them indefinitely should the prey be unable to escape.<br/>Digestion takes a long time. Take the Prey's weight, multiply it by their Constitution, then divide it by the Predator's Constitution, this is how many rounds it takes to fully digest prey passively. These same values apply no matter size difference.<br/>If a Predator wishes to speed up their digestion, they may add their Strength score to their Constitution score before dividing the Prey's Weight x Constitution score.<br/>Observers can also attempt to aid digestion speed by massaging the predator's belly, adding the masseuse's Dexterity score to the predator's Constitution before dividing the prey's weight x Constitution score.<br/>Predators may choose at any time to expel their prey during the digestion process, this takes a number of rounds equal to when swallowing Prey. During this time, the Predator will still be digesting them.<br/>Prey attempting to escape from the stomach need to make Escape combat maneuvers against the Predator's CMD. It takes a number of rounds to escape a predator's stomach equal to the predator's Strength score. If the prey attempts to escape from the mouth, the predator may choose to swallow them again as normal. If the Prey attempts to escape through the intestines, the predator does not get the opportunity to swallow them until after the Prey has escaped.<br/><br/>Rebirth<br/>When a predator digests a prey, they can attempt to bring the prey back via pregnancy.<br/>When a predator attempts to impregnate someone/get pregnant, they must make a will save to reform the prey. The dc for this save is 10 + the prey's hd + the number of days the prey has been digested. Failure means the prey's soul passes on.<br/>Rebirth pregnancy duration is accelerated from normal pregnancy. It takes a number of rounds equal to the prey's age in months to be fully reformed. It then takes a number of round equal to the mother's Strength score to expel the reborn prey from their body.