Prerequisites: Complete Clearing the Landslide, unlock the rest of Meadow Range
Reward: Moon Cloves
Unlocks: The First Chemistry Test
Unknown Residue is triggered once you've cleared the landslide that has blocked off the eastern portions of Meadow Range. Complete Clearing the Landslide, then approach the landslide itself. You'll see that you need 1,500 G, 225 Wood, and 175 Rocks. Collect everything you need and Moonbury's two rangers will clear the path away for you.
Trigger the Heart of Meadow Range Fast Travel point, then follow the path northeast from it until you hit an intersection. Travel south until you hit a three-way intersection. West of here is the South of Meadow Range Fast Travel point, and further west you'll find a conspicuous patch of ugly purple. Forrest will show up to explain what it is - basically he doesn't know - and suggest that you speak to Myer about it.
Track down Myer and you'll have a conversation with him in his office. He'll explain a bit about why everyone hates chemists - one was responsible for that goo pool you saw earlier - and offer to let you investigate his archives. Check the cabinet to the right of Myer's desk and you'll receive a recipe for the Iris Vial, which should clear up the goo.
Head home and you can now brew up a batch of the Iris Vial. The Iris Vial's template requires 16 filled squares, and you can still only use five ingredients. The ingredients you've been collecting from the initial areas of Meadow Range aren't going to cut it this time. Here are some suggestions:
- You'll need either a Bug Leg or a Copper Nugget to fill in the three-block gap in the top-right corner of the template. Bug Legs come from the insectile Crownmites that explore eastern Meadow Range, while Copper Nuggets can be mined from the new assortment of rocks in the same area.
- A slimy thing and some Spores will fill the upper squares nicely. Both can be collected from enemies in the first section of Meadow Range.
- A Bear's Claw and some Black Fur will fill in the lower section of the template. The Bear's Claws can be collected from Honeypaws in the earlier sections of Meadow Range, while the Black Fur is collected from Blackpaws, found west of the gooey patch you're trying to clean up.
Cobble together the Iris Vial and take it to Myer. A cut scene follows, and once it's done the patch of slime will be completely cleared up, allowing some Rainbow Dew plants to grow. Head back home and in the morning Collin, a Capital chemist, will stop by, giving you a new quest: The First Chemistry Test.