Replace many of the current Frostologer Castles with a Chillager Outpost that spawns with a map to a Frostologer Castle

Checklist:

• Add a small Chillager Outpost structure
• Generate this structure in Snowy Plains and Jagged Peaks
• Place a couple of Chillagers in it - but don't have them respawn
• Add a chest with a high chance of containing a treasure map pointing to a Frostologer Castle

Cool inspiration for the design: https://www.artstation.com/artwork/X1yDOn