If you want to find it on your own i suggest that you don't read this!
In the near the tabby gordo slime there are some hexagonal rock pillars. Use your jet pack to fly over these and end up in a place with a wooden bridge to a construction slime gate. On the other side of the gate is probably what will be the glass desert but ignore it for now. You can either drop down from where you are or go the long way across the bridge then back to the bottom of where you were but be careful about the angry pink rock slimes that will spawn once you are near. Now follow the path away from the gate along the shore and enter the cave. Here there is a phosphor gordo slime that will explode into the second key! The area to use the second key has not been implemented yet though, but when it is you'll have the key!
The Phosphor Gordo Slime:
- Phosphor Gordo Slime.png (161.48 KiB) Viewed 1968 times
Thanks for reading, hope this helped! :D