The issue is quite simple really, but we started a campaign where one of the main character drank dragonblood and it started transforming him. He is slowly becoming a sorcerer of the draconic bloodline. However, in order the put it in the story I've designed it as a sort of diseased where he slowly gains his powers but at the same time becoming more and more sick. I've sent them on a quest to find ingredients that will make it possible for an alchemist to design a potion that will stabilize his blood and save his life. My issue is that I've no idea what to make them look for, what type of ingredients would be possible in order to make this potion. Right now they;re hunting for a book in a catacomb library and that's as far as I've gone for what could be possible, but I can't get my head around what to make them hunt for. 

What kind of ingredients would you make them search for? They are level 5 and I'm looking to possibly have them search for either, creatures or various things to acquire.  This is a homebrew campaign, so anything recommendation would be welcomed.

blood of a dragon of the opposite color... so if was red dragon blood, he needs gold dragon blood. A rare flower that only grows at a certain temple in a remote location, the heart of some rare creature, and/or a hair from a celestial being. all kinds of things.

 Well, first I wouldn't put that as a desease but as "spellcasting puberty". Since he is slowly becoming a sorcerer I would just put him struggling against sudden magical eruptions rolling effects from the Wild Magic Surge table and challenge him like maybe asking a WIS saving throw anytime before the unspected effect until you as DM decide he reach control over it.

But as long you already briefed the situation like that, and they ar already searching for that antidote for his desease, I think thats no more time to go back.

So my obvious sugestion is to brew the antidote from the poison, wich means from dragon's blood. Maybe they find I book about that topic that lures them to pursuit a dragon of the same type that the one from the blood he dranks. Maybe it must be from the exactly same dragon it came from.

Another solution may be a bit more fantastic: You can explain that as common reptiles, dragons have a cold blood (I'm not sure if that is a descripion of it in 5E) so the desease is related on his own blood becoming could and his body not adapting fast enought. So, in order to brew an antidote and stabelize it the alchemist needs a spark of dragon fire and than the entire group must pursuit for a dragon to catch it (persuasing it to gift them or not) but first they must find some sort of magic vail that can retain that sparkle.

And if you don't breaf it as an actual alchemy solution I would rather chose a more ritualistic matter: If the original dragon for this blood havn't permited him to drink it, that may be the cause of the desease, like a curse that everybody else who ever drank stolen dragon's blood has faced. So, in order to remove the curse, he must find the original dragon (or ask some shaman/cultist/whoever to perform a ritual to contact it if it's already dead) and ask him for appologize and permission to use it's powers. Of course the dragon must ask him something big in return so you can fill it up with more adventures.

If neihter one pleases you, and you looking just for an amount of differnt materias wich would fit to a brew of that kind, I can suggest you some like: ashes of dragon's bone, a dragon nail, a dragon tear, a sparkle of dragon fire, dust from dragon's lair, ashes of a dragon hunter, iron powder from a Dragon Slayer (magic item) blade. Well, can't think anything that does'nt came from a dragon or a related champion.

Also, you can include a dragon flower (Antirrhinum) as an ingredient, maybe you can say it a flower believed to grow from dragon's blood spilled to the earth (hard places to explore).

Crazy Idea. Find a good and complex cooking receipe, find another name for the herbs. And research where the herbs in real life come from. 

+1 for the quest to either be to find the blood of the same dragon, the blood of a different dragon or some form of monster produce. The options I would consider:

 • Easy: A plant of some sort which is found beyond >insert any series of encounters and travel here<. Go to the place, find the flower, everything's good as long as no-one goes burning the mountain down or something!

 • Moderate: The blood/tooth/heart/concerningly descriptive anatomical part of a monster. Find the monster after >insert some stuff here<, then slay it, rip out its heart, and home in time for dinner.

 • Difficult: The breath, soul, spark or any other hard to get part of a monster. Usually this would rely on the monster needing to be alive to either give the gift or have the gift extracted. Find the monster after >insert jaunty travels with vicious battles here< and then... well, the party will have to work that one out! They can't just go in and kill everything that moves for this one. I have an incredibly open challenge lined up in one of my modules for the party to harvest the breath of a Gorgon. I've left it completely open to them how they do it, and will reward good thinking with success.

So if you were to say to them that they can cure the character with >insert dragony-sounding flower here<, removing all abilities as well, or they can stabilize them with the heart of a dragon of the same type, giving them limited abilities, or they can complete the process with a fragment of a dragons soul (which can only be gifted by a dragon and will bind the sorcerer and the dragon together in a light, can't-summon-a-dragon kind of way) giving them full powers, that would give them options for solving the problem. If they go for the difficult one, then you can make them friendly to the dragon, make them an occasional NPC who is always helpful, and then make something bad happen to them, launching a "save the dragon" quest. If the dragon dies, their powers die too - that's extra incentive.

Because if I were the BBEG, and I learnt that the party were super friendly with one character, then I would go after them to lure the party into a trap. Assuming the BBEG is powerful enough to defeat a dragon!

Remember, just because you set them on a plan because someone thought this would "cure" his "disease" doesn't mean that they are right.  Sure, they go through all the steps, but that wasn't what actually made him stabilize.  Maybe it was the puberty stage.  Maybe it did make a difference and helped him to adapt and the finding of the ingredients just caused enough time to pass for the stabilization to take place (like thumping a coke can so it won't spew out).  Just because the players believe one thing, doesn't make it so.  And just because you set your mind on a course doesn't mean there aren't ways to change course...   

So with that in mind, I kind of like a mix of both.  Play up some of the wild magic effects.  Make them find difficult ingredients.  What they players end up believing may be entirely different from what you know to be the truth... and in the end, the story that comes out of all of it and the hours of fun that was had are the keys to the "recipe".

Ooh, Grayfax has a good point there!

It would work very well to have someone realise the destructive potential of a wild-magic user and send them off to the mountains to spend their puberty on a wild-goose chase, blowing up boulders instead of houses!

They could get back and be told all that mattered was that they were safely outside of civilisation!

Depedning on how much time you want to invest in it, I think I'd do the following:

Step 1: The Sorcerer needs to mix 1 pint their blood (which deals 1d6 hp damage)  with water from a pure/blessed spring. One pint of this mixture must be drunk each day for one week. At the end of this week, the Sorcerer will need to undergo a "ritual of purificiation", this invovles the Sorcerer drawing another pint of their blood (and dealing another 1d6 damage) and having someone perform a level 1 Purify Food & Drink spell as a ritual on the mixture (you could also have the Ceremony spell required as part of this as well). Make a note of how they mix their blood with the spring as well, if they just cut themselves and bleed into it then consider having the spring "tainted" which might give you a plot point to return to later.

Step 2: The Sorcerer must travel to a shrine to a Draconic Deity and perform "The Three-fold Ritual" to draw the Gods attention. This ritual represents Knowledge, Understanding and Strength of Will. The Sorcerer does this by performing three spells of their choice which they feel represent the draconic power they have been gifted/given. Each spell should be of a different level and they cannot choose the same spell twice (cantrips can be used). After they cast the first spell ask them to say what they do during the casting and what any on lookers see, then have then make an Arcana Check, this represents Knoweldge. After the second spell, again have them narrate what onlookers see or what they do and have them make a Religion check, this represents Understanding and finally after the thrid spell have them make a Performance check to represent their Strenght of Will. The DC of each check should be challenging so would suggest DC15 unless they have massive bonuses or penalties, it should also be noted those checks relate to Intelligence, Wisdom and Charisma which govern the three main forms of spell casting. If the Sorcerer can succeed on at least two of these then an Avatar of the Deity appears and blesses the purified sample of blood and congratulates the Sorcerer on their successful ability checks and repreimands them on any failures. If they fail all three then maybe have some sort of punishment sucha s a Elemental summoned in to chase the Sorcerer away. Once this ritual has been successful the Sorcerer drinks the mixture. If th ritual fails then they can repeat it after a period of time has lapsed.

You could end it there, but, if you wanted to go for something a bit longer then....

Step 3: In order to fully cleanse themsleves and master their Draconic infused blood the Sorcerer must submit themselves to a "Test of Fortitude". This requires them to be afflicted with a Contagion spell or similar effect. Successfuly resisting the effect enhances their previously purified and blessed blood.

Step 4: The final ritual. They must travel back to the Shrine from step 2 (or a different shrine if you want to send them to another place to drive other plot points). Once there, they must defeat a chosen avatar fo the Deity to show they have the Strength to fully master the draconic blood. Assuming they are still level 5, this avatar could be an Elemental, a Violet Faerie Dragon or Chromatic Gaurd Drake. This fight should be one on one. If the are successful then the Avatar from step 2 appears and blesses the Sorcerer and casts Greater Restoration which purifies the Sorcerer for the final time.

This last bit might not be completely fair but, should the person playing the Sorcerer roleplay each stage of this ritual really well, then I would likely also give them the Find Familiar spell as a bonus spell and let them use it to summon a Pseudodragon familiar as a reward.

these are all fantastic ideas, I already have a few ideas brewing! I found a really cool homebrew module with monsters from bloodborne that would be great with the setting I'm developing.

I like the idea that he needs more blood from the exact same dragon but there is an extra catch - it has to be freely given.

Hijinks ensue.