"Oh if these caverns could talk... my, my, my, what stories they'd have to tell! Now all they say to me is, don't go messing with forces you don't understand!"
The Ancients existed along time before PMW3's plot and inhabited many regions, from the Banni Wastelands to the Cragstone Mountains. They built structures such as puzzles and the Cragstone Bridge. They wanted so much power that they started manipulating the Spectral Realm, unintentionally breaching its meniscus (unlike Erwin who does that on purpose). They created the Ancient Defenders and had many sacred rituals. They tried to use the Spectral Energy, causing a massive explosion that wiped them out and left their temples and catacombs ruin. Archaeologist, including the friend of Pac-Man, tried studying their lives and history but state they know almost nothing about them. Close to the mountain ruins is the Windmill Village, which might have been built by another future civilization, because the windmills are in a great conditions, meaning it was built more recently.
During the Events of Pac-Man Wolrd 3
"Mysterious forces? Do you mean the Spectral Realm? Is this why Erwin is siphoning down here?"
Erwin build some Siphons in the Cragstone Mountain range, which is considered weird by Orson, other places being much better for placing Siphons than the mountains. The only possible reason for that location is the remaining energy from the explosion.
- The Ancients had dynamite, as seen when travelling in the ceiling.
- If you stand on the edge near the Siphon or closer to the entrance, a huge structure above the clouds can be seen. Although not on fire, it may be Gogekka Heights before being set on fire.