How to get there
Enter Ancient ObservatoryOpen on the map- "Enter Ancient Observatory" from Overworld
About
The world map marks the Ancient Observatory south of Kal Crossing, near The Boiling Loid and the Observatory Town Ruins. Inside are a necromancer, zombies and a skeleton, along with a few men.
No quest or dialogue names this building. The game does tell of an occultists' observatory in the same part of the world, in From Nothing, though that story never says it is this one. Theodore Badon suspects occultists of the disappearances on the south road, and tells you "The observatory is up the hill". The quest log sends you to "learn the password used to enter the occultists' observatory", and a slip of parchment dropped by an occultist spells it out:
"STOP FORGETTING IT." "BYTHOS FILLS THOSE WHO ARE WORTHY."
Those locked in its cells tell you what they went through:
Algernon the Wise has the key to our cells, you'll have to find him and take his key to free us. Please hurry, they have been doing horrible things to us one by one...
Afterwards Theodore introduces you to Captain Balor as the one who "aided me in the raid on the occultist hideout near the Boiling Loid."
Creatures
Numbers count spawn points, not creatures alive at once.
Cavern Netting Spot
Guilded Unlocked Chest