What is the point of the broken essence key? I've checked every mixing station and there is nothing... Is it's purpose not implemented yet or am I just dumb? also in the caves the area where the question mark is, It says you need a stronger evolution I'm at Zeta, is this for a later update or is it bugged?
The section in the cave is going to be connected to another form based in pure strength, the Zeta is based in Lust and magic. Should be added on a later date!
The broken essence key can be completed with the Essence Summoner's plug in your room's mixing/crafting station if you have unlocked a personal house. It can be used to open the gate in the essence caverns where Slimette resides.
Confirm the following:
1- You are in one of your unlocked apartments (Nem'yh or the Goblin bog)
2- You are clicking on the top right tab of the crafting menu for the key items crafting.
If its not appearing, or the tab is not appearing, please send me a screenshot of the crafting screen you see, alternatively you can send me a link to your save file. I want to figure what happened out so you can unlock it.
EDIT: I found something, If your safe is old, and you completed the Essence caverns before the Slimette patch, this could have caused the issue, let me know if this is the case.
I have replayed from a clean safe a couple of times and the problem does not seem to appear, my guess is that in-between updates and your save file something might have untriggered the condition required to have the crafting option, this could happen in rare cases depending on when your save was created and what changes have been applied since. I have implemented a redundancy trigger upon defeating the Summoner slime again after the mission. This should allow you to fix the save file check by fighting the boss again. This change should be up and ready on the next patch. The game is pretty much still on Alpha and stuff like this could happen between updates, thank you for reporting it. In the meantime, if you wish to try out what the key unlocks before the next patch, you can start a new save. On the bottom right of the world map there's a blue tree that allows you to access the cheat room. There you can make up for a lot of lost progress if needed. If this is a specific version bug, and the problem persists even at a new save, do let me know, I'll try to cook an early patch for you.