Stardew Valley: How to obtain Prismatic Jelly and where to use it
When you boot up a game with such a wholesome name like Stardew Valley, you expect to have a pretty relaxing time. Sure, it's hard work running a farm by yourself or with a few friends, but it's satisfying nonetheless. The more you work on it, the more notice the villagers will take as you start to become a pillar of their community. Of course, this means they'll also count on your help to fulfil some of their requests, some of which require you to slay monsters in the various danger zones. Play long enough and you'll be sent on a quest for Prismatic Jelly.
This is one of the few items that is quest exclusive and you'll need to wait until that quest is active before you can obtain it. That being said, it's definitely one of the rarest items in the game so you may not get it right away. Not to mention that it requires you to hunt down slimes, one of the most numerous and frustrating enemies in the area. With the right amount of luck and enough perseverance, you'll find the slime you need to get your hands on the fabled Prismatic Jelly.
What is Prismatic Jelly?
If you've been playing Stardew Valley for a short amount of time, you've likely come across Slimes. They can appear in any dungeon at any time and are likely to drop Slime, which can be a pretty useful ingredient for crafting. You'd better get used to slaying them since you'll need to look for them to get the Prismatic Jelly. This item appears as a glass jar that is filled with a rainbow-coloured slime substance.
Despite how rare it is and undoubtedly has magical properties, there's only one person who wants it: The Wizard. He appears to be the only person who can use it too since no other Villagers want or request it. There's even a glitch on the PC version of Stardew Valley that proves that everyone except the Wizard hates to get it. Not even you can use or sell the Prismatic Jelly and once you've completed the quest, you'll never be able to get it ever again.
How to get and use the Prismatic Jelly
There are quite a few things that need to happen before you can start hunting for the Prismatic Jelly. The first is that you need the right quest to appear and this simply takes time. There are no prerequisites to unlock or speed up the appearance of the mission, you just need to wait. When the time comes, the Wizard will request a special order simply called "Prismatic Jelly." When it does appear, you need to accept it and thus Prismatic Jelly will be added to the drop list. 
Now, you need to go spelunking. Slimes will appear in either The Mines, the Skull Cavern, or the Quarry Mine. The only dungeon where you can't find slimes is the Volcano Dungeon on Ginger Island, which at least saves some searching time. What you're looking for is a specific slime known as the Prismatic Slime. Even when the quest is active, the Prismatic Slime is extremely rare.
It has a chance to appear in any of the designated dungeons at any time and on any floor but only has a 1.2 percent chance of doing so. The only thing you can do to boost your chances is to wait until your Daily Luck is high and head into the dungeon as early as possible. If your luck is poor, you shouldn't even bother to look for it until it improves. The Quarry Mine is recommended since if you spot the slime but are forced to leave, the slime will remain there until the day ends.
While looking among the slimes, you need to look very carefully. The Prismatic Slime doesn't casually pop out but is still noticeable. Its biggest distinction is that it will gradually change colours over time, cycling between all the different slime colours. It doesn't glow or anything, so be extra observant when finding slimes in dark spaces. When you do find the Prismatic Slime, you'd better be ready because it's one of the toughest enemies you'll ever fight.
Not only does it have a lot of health, but it can deal a lot of damage too. Make sure you fight the Prismatic Slime in an open space and use a weapon that has extra reach to strike it from a safer distance. After you defeat it, it'll drop the Prismatic Jelly for you to collect. The only exceptions are if the Prismatic Slime has replaced a Special Slime and won't drop it or you're wearing the Burglar's Ring, in which case you'll get two Prismatic Jelly.
After you've got the fabled rainbow goo, you can make a beeline for the Wizard's Tower. Talk to the Wizard to hand it over and you'll be generously rewarded with 5,000 Gold and the recipe for Monster Musk.
