I’m not retelling the Horus Heresy plot here—I’m explaining how it *came to exist* in the first place, and it starts in a place you wouldn’t expect: 1984’s BattleDroids (later Battletech). That game showed one way to sell a miniatures-adjacent system: go wide. Tons of different units, lots of standees, and if you want a specific mech in metal you hunt it down. The problem is, war gamers don’t behave like normal shoppers—if the exact thing they want isn’t on the shelf, they don’t “just grab another candle.” They leave, and retailers get blasted in the face by a product line that’s too wide to stock properly. Games Workshop’s answer was to go deep. Brian Ansell wanted giant robots, but he wanted a product that actually worked for stores: one plastic Warlord Titan kit with a shared frame and a pile of weapon options, meaning endless variants without endless SKUs. That created a new problem—if everyone’s using the same robot, how do you make it feel like a war? Jervis Johnson’s solution was background: a civil war, seeded from a throwaway Rick Priestley quote about Horus, then expanded into Adeptus Titanicus, Epic, the early Heresy board game, 2nd ed codex lore, Index Astartes, Black Library’s Horus Rising, Forge World’s Betrayal, and finally the modern plastic Age of Darkness era. In short: the Heresy is as much economics and tooling as it is tragedy and betrayal.