While the book is branded with Stars Without Number, the mechanics are generic. The mass combat system uses "Hit Dice" bands. A unit of 20 goblins (1 HD each) fights as a single "Warband" with 20 hits. This keeps the game fast.
Before we discuss the PDF, we must understand the artifact itself. Published in 2013 by Sine Nomine Publishing, An Echo Resounding is a 74-page supplement that bridges the gap between small-scale adventuring and large-scale strategic conquest. an echo resounding pdf full
I should also think about examples from literature or philosophy that deal with echoes. Maybe reference Plato's "Allegory of the Cave," where the echoes represent the illusory world. Or mention how in modern psychology, the concept of priming shows how past experiences affect current behavior, acting like echoes. A unit of 20 goblins (1 HD each)
Resounding Through the Ages