I understand from the wiki that shadow lair materials based on the boss fought are found in sanctuary. The wiki doesn't specify whether there is a chance of acquiring the material, or if it is a guaranteed thing. Could someone with experience please clarify?
Question on Shadow Lair Materials
Once you defeat the boss, you have to go through Unknown Passage to get to The Sanctuary. The Sanctuary holds the material and there will be a machine there. You are guaranteed the material if you pass through the whole Shadow Lair.
What happens if you go all the way through a Shadow Lair, fight through the Unknown Passage, just barely surviving, but have little Energy and Crowns left once you get to the Sanctuary?
You'll still have the material but not be able to craft if you don't have everything at end. Then you'll need another trip (and thus another mat) to be able to craft at this special alchemy machine (it's not the same than standard ones).
Speaking of which, I'm assuming the Sanctuary machine has the same crafting costs (5k/800cr pp) as regular machines?
Yes.
http://wiki.spiralknights.com/Sanctuary_Alchemy_Machine
Also the mat is floating there, you have to pick it up. You could easily miss it if you dont pay any attention.
It is guaranteed that you get one material depending on which boss you beat.
So, if you beat the shadow snarbolax everyone in the party gets one Nightmare Mane each.