Scale Rot

With the creation of The Elefae, the archfae and primordials also created a series of lesser dragonkin. Their mortal forms held through most of the fighting, however, with Hraedrek's descend into madness a sickness began to take hold. The magic grafted onto these mortal bodies could not handle the magical backlash as one of their deities fell to madness. By the end of the war, a few members of the Drek Guard had begun to show signs of corruption. After the war was won, these individuals began to fall into a deep sickness where the prominent symtom included their scales losing color and eventually turning a deep shade of purple. Some of the more unfortunate individuals would develop mutations and descend into madness. After the dust settled fromt he giant war, those afflicted the most turned on their brethren and had to be killed for the saftey of the clan. Druids and Clerics came together to help stabalize the sickness in those already afflicted, but they still had to be sent from their kin so that they did not spread the sickness to other dragonborn.

Spread & Prevention

Scale Rot is a rare, but terrifying disease the the Dragonborn people. It robs many of them of their deep need of community and clan. Little is known about the transmission of the affliction. Only that it is passed on in moments of intense emotion, and that only those of draconic blood can contract it. No cure has been found, other than the use of a Wish spell.

The fear of this condition has been ingrained in the hearts and minds of the dragonborn. Once a proud and boisterous people, within a generation the threat of this disease has caused them to learn how to control their emotions better than any other race. They are taught to avoid intese feeling, and have become known as the most stoic people within Elturia. All to reduce the risk of the transmission of this disease, since they are never really sure who carries the magical illness.

Wyvern affected by Scale Rot

Wyvern by Annette

Stages

The condition moves slowly at first, but as the individual gets into Stage 3 and 4, the condition begins to rapidly get worse. A few dragon born will seek out the disease, wanting the power it holds. The farther one progresses down the disease, the harder it is to control one's emotion.

Consult with your GM for what feels appropriate in increasing to the next stage. The GM may wish to keep it secret, asking for a saving throw if the player shows intense emotion in the character, or they may wish to be more explicit. The player should at least be aware that increasing in stage has something to do with strong emotion, contact with another afflicted, or Hraedrek's direct influence.

Stage 1

Not many visible symptoms. At times times, the infected may have terrible headaches or slight fever. The may have trouble sleeping, or swear they hear a voice, or even see somone that is not there. However, they seem to have the uncanny knack to see through illusions. Most will not recognize the disease at this stage, only scholars or other dragonborn trained to spot it.
You gain the following benefit: You may roll with advantage when determining if something is an illusion.
You also gain the following detriment: At the start of each day roll a d20, on a 5 or lower you are suffering from a migraine or some other symptom. Choose between Wisdom (Perception), Intelligence (Investigation), or Charisma (Pursuasion). Subract 1d4 to your chosen skill until you complete a long rest.

Stage 3

Most people begin to realize that an individual is afflicted with some sort of disease at this stage of the disease. The individuals scales begin to lose their original color, with the purple growing more prominent around the edge of their scales. The dragonborn will also develop visible lesions. Greater Restoration or similar magic will reduce you to a previous stage of the disease.

You gain the following benefit: Your breath weapon becomes ibued with the nature of your affliction. You deal an extra 2d10 psychic damage when you use your breath weapon. Additionally, if you encounter a language that you have not learned, roll a d100. If you roll less than your level you learn the language instantly. You forget the language if you are healed to a previous stage.
You gain the following detriment: Your charisma score is reduced by 2.

Stage 2

Almost any dragonborn will notice the disease at this stage. Slight discoloration of the scales begins to show at this stage. The afflicted will also develop some sort of malady of the mind. Their penchant for seeing and hearing things that are not their becomes worse. Lesser Restoration or similar magic will reduce you to a previous stage of the disease.
You gain the following benefit: You can cast detect thoughts once per day without expending a spell slot. After you cast the spell in this way you may use any spell slots of first level or higher to cast the spell.
You gain the following detriment Roll a d6, you gain the following madness until you are reduced to a lower stage.

1. The character regards something with intense revulsion, as if affected by the atipathy effect of the antipathy/sympathy spell.
2. The character becomes attached to a "lucky charm," such as a person or an object, and has disadvantage on attack rolls, ability checks, and saving throws while more than 30 feet from it.
3. There is only one person I fully trust, and only I can see this special friend.
4. I don't like the way people judge me all the time.
5. I try to become more like someone else I know adopting his or her style of dress, mannerisms, and maybe even name
6. I am convinced that powerful enemies are hunting me, and their agents are everywhere I go. I am sure they are watching me all the time.

Smoke by Rachel Burkum

Stage 4

At this stage, the individual afflicted becomes entirely spurned by society if they do not hide the nature of the disease. The chaotic nature of the affliction manifests differently in each individual, but they all share one thing in common. Dragonborn that reach this stage develop a mutation that erupts from the lesions on their body. Some develop scally wings, others a more potent breathweapon, or even an extra limb. At this point the afflicted realize the things they saw, the voices they heard was at the will of the Hungering Dark. You may only be reduced to a previous stage by means of a Greater Restoration spell, and the spell caster succeeding a DC 18 check with their spell ability modifier or similar magic.

You gain the following benefit: Roll a d6 to determine what gift the Shackled one has bestowed upon you:

1. Your throat bulges, and a strange colored liquid seeps from the corner of your mouth. Increase the range of your breath weapon attack to 30 feet, and increase the damage by 1d10
2. You grow a pare of glowing purple spectral wings, gaining a flight speed of 30 feet.
3. You grow an extra arm, increasing the number of attacks by 1
4. Your brain grows in size, forcing your scales to grow around it. As a bonus action you may assault the mind of a creature, forcing it to make a concentration saving throw on any spells it may be concentrating on. Additionally, the creature has disadvantage on their next attack
5. The air around you has the faintest hue of purple. You gain the ability to to channel the madness within you, forcing creatures of your choice within 30 feet to make a DC 17 charisma saving throw or become frightened of you for 1 minute. The target may repeat the saving throw at the end of their next turn.
6. Hraedrek's crest appears glowing in front of your forehead at all times, shedding dim purplish light for 10 feet. You gain the ability to speak telepathically. Additionally, you may cause the symbol to flare. You are able to cast the Dominate Person spell a number of times equal to your modifier. After the spell fades, the individual must make a Charisma saving throw or suffer from a Long Term madness. Roll on the Long Term Madness Table in the DMG

You gain the following detriment: There are no additional detriments at this stage. However, Hraedrek's influence becomes hard to resist, and curing the affliction becomes incredibly difficult. Work with your GM on how to implement this in your game.

Stage 5

Very few ever reach this stage of the sickness. The individual that gets to this stage is forever lost to Hraedrek, becoming his champions. His gifts are showered upon them, becoming unrecognizeable and shells of their former selves. They can only be saved by the Wish spell or similar magic.
If a player character reaches Stage 5, they become an NPC under the control of the Game Master.

Affected Groups

Outside of true dragons, all creatures that have any draconic blood have a chance to be affected by the affliction. The groups that are affected the most include dragonborn, kobolds, near true dragons, and draconic sorcerers.

Hosts & Carriers

Various creatures are possible carries of the disease, particularly those with draconic ancestry. The more draconic blood that flows through the creatures veins the more likely they are to exhibit symptoms. For example, a draconic sorcerer that has a dragon ancenstor far back in their family tree are likely to only be carries of the condition. However, if their parent or even grand parent was a dragon or other dragonkin they are more likely to show symptoms.

For nonsapient draconic creatures that are close to true dragons, such as a wyvern, they will experience many of the same symptoms as a dragonborn that are affected with the disease. However, they lack to ability to control their emotions, making them incredibly dangerous to other dragonborn.