The decent into Hell is not an easy one - it takes its toll on both the body, and he mind. But the ancient evils that dwell in this place are enough to change you, in body, mind, and even soul. It may turn you mad, it may disfigure you, and it can even turn you against your friends and loved ones with its lures.
Corruption is an optional rule that can be applied to the game. It has both system and story mechanics that can change the style of game you play. Certain items automatically impact upon this system, as well as any actions that you, the DM, feel can contribute aswell. For example, harming an innocent NPC, or making deals with the creatures in the Cathedral depths.
Corruption is independant of PC levels, and can grant boons dependant on how how Corrupted a PC may become.
If you use this mechanic in your game, every act can contribute to each player's corruption counter. Each player is responsible for keeping track of their assigned Corruption form, and their Corruption scores.
Forms of Corruption
There are three forms of corruption in Diablo: Decent into Hell; Bloodlust, Madness and Decay. Each form of Corruption works iand affects players in unique ways. Once a player has been affected by one type of Corruption, they cannot be affected by another, but they can still accrue corruption scores from that source.
Bloodlust. The smell of blood becomes sweeter, the sounds of flesh tearing becomes music to your ears. You no longer desire talk, and negotiation, they only get in the way of what you really, truly want. From now on, you only take your steak bloody.
Madness. You swear that statue just winked at you. No-one else believe you, but since it's now laughing at you, it can't be denied. The others tell you that you're seeing things, but you know the creatures in this place are telling you things, things that only you can understand. I know, other me, they obviously don't have the gift.
Decay. Your joints creak as you walk, but the cold no longer bothers you. Sleep no longer comes easily, but then again, you don't feel you really need it anymore anyway. Everything around you seems to slowly die, even the grass will wilt if you stand in one place for too long. Not that you care, to be honest.
Throughout the game, players will interact with many different sources of Corruption. These can be anything that you deem to be corruptive, such as choices the players might make, interactions with paricular characters or creatures, or taking posession of particular items they find within the Cathedral depths.
Each item flagged as Corrupted is assigned a specific Corruption type and value. When a player claims a Corrupted item, they gain Corruption points equal to the value stated in the item's description, and unless they already have a Corruption type, they also gain the Corruption type of the item. For example, The Mad King's Crown casues 2 points of Madness. If a player takes this item, and gains 2 Corruption points, and if their previous total was 0, they then gain the Madness Corruption type.
Choices and Interactions
Players interacting with the world can be unpredictable, but that can be embraced. If a player makes a choice that you feel is Corruptive, you can award them Corruption points, and an appropriate Corruption type, if applicable. If you don't feel a their is an applicable type, choose on at random, or ask the player which one they might want.
Everything within the Cathedral has an impact upon each player's corruption levels. Demons, and the evil magics within the place, all play on a person's soul. Even making the wrong choice can push the players further into darkness. When a player reaches a new tier in the Corruption scale they gain the effects stated below.
When a player reaches 10 points they must make the appropriate changes to their character sheet based on their assigned corruption. Read the appropriate alteration to each player:
The Corruption has set in, and is beginning to take effect.
Bloodlust. Increase your Attack and Damage modifiers by 1, and decrease your AC by 1. The adrenaline of battle gives you strength, you can feel your blood pumping almost constantly. Your aggression makes you hit harder, but in disregard for your own safety. This effect increases with each Tier.
Madness. Increase your Perception by 1, and decrease your Initiative Bonus by 1. Your gaze is always shifting, jumping from shadows that flicker in the corner of your eye, to statues in the shadows. Unfortunately this distraction keeps you preoccupied, taking longer to bring your focus back to the situation at hand. This effect increases with each Tier.
Decay. Whenever you take bludgeoning, piercing, or slashing damage, reduce it by 1 for each hit. Additionally, when you roll a hit die to recover your hit points, reduce the overall total by 1. Your physical senses appear to be dulling, causing you to be less affected by physical sources of damage. However, recovering from damage seems to take longer. This effect increases with each Tier.
When a player reaches 20 points they must make the appropriate changes to their character sheet based on their assigned corruption. Read the appropriate alteration to each player:
The Corruption has taken hold, and is beginning to show on a physical level.
- Bloodlust. You have advantage on all Strength checks and saving throws, and disadvantage on all Dexterity checks and saving throws. Your muscles are beginning to swell and bulge in a grotesque form, but your bulk is making it difficult to move as easily.
Madness. You have advantage on all Wisdom checks and saving throws, and disadvantage on all Intelligence checks and saving throws. You notice things no-one else does. Things moving in the shadows, and whispers floating on the air. Reality, however, seems to make less sense. Or, does it? Maybe everyone else are the crazy ones?
Decay. You have advantage on all Constitution checks and saving throws, but disadvantage on all Charisma checks and saving throws. You are becoming skin and bone, like an empty husk. You care little about outside interactions from damage, to fatigue, to others trying to influence you in any form.
When a player reaches 30 points, they must make the appropriate changes to their character sheet, based on their assigned corruption. Read the appropriate alteration to each player:
The Corruption is a part of you now... give in... you know you want to.
Bloodlust. The smell of blood is intoxicating. You can consume blood of any creature, other than yourself, to recover d10 hitpoints, plus your Constistution modifier. You can use this ability 3 times per long rest. Each time you use this ability, you automatically gain 2 Corruption Points.
Madness. The walls have begun talking to you. You can communiate with any inanimate object - statues, chairs, or dead creatures, and ask The DM one question about the current floor of the dungeon. You can use this ability 3 times per long rest. Each time you use this ability, you automatically gain 2 Corruption Points.
Decay. The air around you has become dry and still. You can add an additional d6 necrotic damage to any attack you make, and apply the "poisoned" condition to the target(s) of the attack. You can use this ability 3 times per long rest. Each time you use this ability, you automatically gain 2 Corruption Points.
When a player reaches 40 points, they must make a saving throw vs Corruption. If a player makes three successes, they drop to 35 Corruption points. If they roll three failures, they succumb to the Corruption, and are transformed into a demonic creature, based on their form of Corruption.
The DC for the save is 10, modified by their Corruption points above 40. For example, if a player has 42 Corruption points, the DC is 12.
When a player reaches this point, roll Initiative (if you have not yet already). If the rest of the party wishes, they can also interact with the PC making their saving throws. Items that remove Corruption (see Removing Corruption) can assist with these rolls.
If the player should drop below 40 Corruption points during this cycle, this also affects the DC. For example, if the PC drops to 38 corruption points, this reduces the DC to 8. Additionally, the next success they roll automaticlly ends the cycle. If the player rolls 3 failures, they lose the PC to Corruption, at which point it transforms, and is replaced by one of the creatures below, based on the type of Corruption the PC had.
The PC loses all gear and equipment they had, which can be found on the corpse of their monster upon defeat.
- Bloodlust. Incredible agony is all you can feel as your body transforms. Your bones crack and bend, your skin tears and your muscles expand, and your vision goes red as you scream, and your screams translate into an unearthly roar. None of this matters to you, however. All that matters is your desire - your need for blood.
Replace the PC with a Bloodbeast (refer Appendix)
- Madness. Your vision starts dancing and blurs as your mind starts breaking down. The truth is revealed to you - your allies were lying to you the entire time - these creatures, these humans only want your death and the destruction of your masters. They must be destroyed!
Replace the PC with a Mad Caster (refer Appendix)
- Decay. A cold presence enters you, taking you over. You watch, unperturned, as it takes control of your limbs, of your body, and your soul. You wath as it trasforms you - your body elongates, your legs replaced by a tail, your chest spits into a maw and your arms split and morph into shapr talons. Nothing matters anymore, as you submit to control of the creature that now owns you. You are forevermore, an eternal servant.
Replace the PC with a Death Spitter (refer Appendix)
You cannot resist the Corruption in the Cathedral, but for those that value the sanctity of their souls, it can be purged. Restoring faith in humanity though your own actions, and carrying out acts of sanctity can remove the Corruption, a bit at a time.
If a player's corruption level drops below the threshhold of a Tier, they lose the effects of that Tier. If a player drops to 0 Corruption, they are untainted, and can become corrupted by another Corruption form.
Choices and Interactions
Similar to how certain choices and Interactions can cause corruption, others can remove it. Depending on who the player(s) are interacting with, and what they are doing, can affect just how much the interaction can affect their Corruption levels.
Holy writings can be found in bookshelves throughout the Cathedral Depths. These scriptures have d4+2 uses, and each use removes d4 Corruption points. These scriptures can be taken for later use.
Within the Cathedral, there are fonts that have not been tainted by the evil powers that dwell there. These fonts contain d4+2 uses, and each use removes d8 Corruption points. Holy water can be bottled, and each bottle stores 1 use.
Statuettes and insignia can be found within the Cathedral. Players must spend 10 minutes praying infront of these icons to remove Corruption. Once a PC has performed this action, the icon becomes useless to them.
- Below Tier 1 this removes d4 Corruption.
- At Tier 1 this removes d6+1 Corruption.
- At Tier 2 this removes d8+2 Corruption.
- At Tier 3 this removes d10+3 Corruption.
These cannot be used on PCs at Tier 4 or above.