Stronghold Builder's Guidebook by Matt Forbeck

A practical, game-focused handbook that walks a dungeon master and players through designing and running fortified bases and lairs, covering everything from architectural plans and room-by-room layouts to construction costs, materials, labor and upkeep, plus rules for hiring staff, recruiting troops and equipping defenses. It presents mechanical options and guidelines for adding traps, siege engines and magical protections, offers sample stronghold types and floor plans for different character levels, includes new monsters, magic items, spells and adventure hooks tied to holding territory, and supplies random tables and campaign advice for sieges, diplomacy, domain benefits and ways a stronghold can drive adventures and character advancement.