Adventure Title
Jewel/Gem/Amulet of (the) Circle/Ring/Obelisk/Column

Alternate title
Ghost/Spirit/Specter of the Forest

Opening Scene
A sewer system that is Tempestuous where they encounter Royalty that is/are Looking for new slaves

Plot hook and draw
An ancient prophecy that is/has Delivered outrageous demands

Plot Concept
Tear a gateway to an ancient era that is motivated by Protect interests

Primary Antagonist
An otherworldly entity Ancient or Otherworldly who/that is Psychotic

Plot fulfillment and location
A stone circle from A sacred temple