For those of you incorporating elements of the Horror Adventures book, I came up with a corruption that might work well if any of your players go down a darker road at some point.
This is essentially a variant on the ghoul corruption, but I added elements of the seeded creature template therein.
Catalyst
Seeded corruption stems from a desire for forbidden lore and dark rituals never meant for mortal minds. It can also be contracted through knowledge of the Great Old One Xhamen-Dor.
Progression
You have a desire to share forbidden lore with suitable hosts. Each week, you must share the knowledge of Xhamen-Dor with another sentient creature and spread the seedborne infection to them.
After a week, if you haven’t corrupted another creature through some other means you must succeed at a Will saving throw (DC = 15 + your manifestation level) each day until you’ve spread enough of the infection. If you fail the save, you feel a burning desire to discuss the lore of Xhamen-Dor. When in this state, if a creature listens to you speak about Xhamen-Dor for at least 30 minutes, they must make a save against the seedborne consumption manifestation, even if you do not possess it. Additionally, the next time you sleep you emit a cloud of spores that expose other creatures within 30 feet to seedborne consumption (DC = 10 + ½ your HD + your Charisma modifier). If you corrupt an innocent creature through either of these methods, your corruption progresses to the next stage.
If circumstances make it impossible to spread the infection you start to slip into madness, taking 1 sanity damage per hour, and you continue to desire spreading the infection until you infect at least 1 creature. If your allies are able to restrain you and provide sentient creatures to corrupt, your corruption doesn’t progress. However, the DC of the Will save against your corruption progressing increases by 2. These increases stack each time this occurs, and they last until your corruption reaches the next corruption stage.
In addition to sharing knowledge, you can’t resist attempting to discover dark secrets. Whenever you are in a library or see a book or journal you’ve never read, you must spend time reading to extract any potential secrets you can.
Corruption Stage 1: Once you corrupt 1 suitable host your alignment shifts one step toward evil and spells that detect undead or plants sense you, though the peculiar result they return informs the caster that you’re still a living non-plant creature. Other spells and effects don’t treat you as undead or a plant. You can use speak with plants at will as a spell-like ability.
Corruption Stage 2: The second time, your alignment shifts another step toward evil and you are affected by spells and abilities as if your creature type were undead or plant (including effects like bane and the favored enemy class feature). This doesn’t grant you any of the immunities of being undead or a plant, nor does it make you immune to effects that target living creatures or change how negative and positive energy affect you.
Corruption Stage 3: The third time, you become an NPC seeded creature under the GM’s control.
Removing the Corruption
Curing a seeded creature requires a special occult ritual to remove the parasitic infestation or use of a miracle spell.
Manifestations
Lurker in Darkness
Gift: You gain darkvision 60ft. If you already have darkvision, this increases your darkvision by 30ft
Stain: You take a –4 penalty on saves to resist seeded corruption.
Fungal Armor
Your flesh is unnaturally tough.
Gift: You gain a +2 bonus to your natural armor. At manifestation level 5th, this bonus increases by 1.
Stain: Your body begins to decay and makes it harder for you to move. You take a –2 penalty to your Dexterity score.
Fungal Defense
Gift: You gain channel resistance +4 and damage reduction 5/bludgeoning or slashing.
Stain: You take a –4 penalty on Fortitude saves to resist diseases.
Improved Fungal Defense
Prerequisite(s): Fungal defenses, manifestation level 5th.
Gift: You gain a +4 bonus on saving throws against mind-affecting effects, cold resistance 10, and electricity resistance 10.
Stain: You take a –2 penalty to your Charisma score.
Greater Fungal Defense
Prerequisite(s): Improved fungal defense; manifestation level 8
Gift: You gain fast healing 5
Stain: Whenever you take damage from a positive energy source, you are frightened for 1 round.
Fungal Limb
Gift: You grow an extra limb. This functions as a tendril secondary natural attack that deals 1d8 bludgeoning damage. You also gain a climb speed equal to your base land speed. Your tendril also has the grab special ability and a reach of 10 feet. Attacks with your tendril are treated as evil and magic for the purposes of overcoming damage reduction.
Stain: You are treated as an undead creature when subjected to channel energy, cure spells, and inflict spells.
Insidious Mind
Prerequisite(s): Seedborne consumption, Manifestation level 4th
Gift: When you succeed a saving throw against a psychic charm or compulsion, or any type of mind-affection spell or spell-like ability your dreams of dark lore infect the spellcaster’s mind exposing him to your seedborne consumption.
Stain: You take a -2 penalty to your Charisma score
Extra Fungal Limb
Prerequisite(s): Fungal limb, seedborne consumption, manifestation level 6th.
Gift: You gain an additional tendril. Your climb speed increases by 10 feet. Additionally, when you succeed at pinning a foe, you can spend a swift action to tie up the foe with a tendril. Doing this causes you to lose 1 tendril attack and you can only have one creature tied up at a time. Every round they remain tied up they are exposed to your seedborne consumption manifestation. The tendrils have hardness 5 and 10 hit points. If a creature tears free or destroys a tendril, it grows back in 1 minute.
Stain: You take a –2 penalty on attacks with manufactured weapons and on all ranged attacks.
Death Burst
Prerequisite(s): Manifestation level 7th, improved fungal defense, seedborne consumption
Gift: Your seedborne consumption DC is increased by 2. When you fall below 0 hitpoints you release psychic spores and all creatures within 30ft of you become exposed to your seedborne consumption manifestation.
Stain: The flesh on your hands is covered with pustules and fungal growths. The penalty you take on ranged attacks and attacks with manufactured weapons increases to –4.
Seedborne Consumption
Prerequisite(s): Manifestation level 2nd.
Gift: Natural or touch attack; save Fort DC = 10 + 1/2 the seeded one’s HD + the seeded one’s Charisma modifier; onset 1 month; frequency 1/month; effect 1d2 Charisma damage (this damage cannot be healed while the creature is infected); cure 3 consecutive saves.
When a creature’s Charisma is reduced to 0, instead of becoming unconscious it falls into a feverish mental state where its mind is scattered and inattentive. The creature can still move and perform actions, but it can concentrate on only a single action, and for only a few moments. It takes a –4 penalty on saving throws; Intelligence-, Wisdom-, and Charisma-based checks; and skill checks. Within 24 hours of a creature’s Charisma score reaching 0, it dies and rises as a seeded creature.
Stain: The stench of the spores flowing within you allows creatures with scent to notice you from twice the usual distance, and makes it extremely difficult to disguise yourself. Any living creatures that have a sense of smell have their starting attitudes toward you reduced by one step. Your supernatural scent is not affected by the negate aroma spell.
