What does *that scene* at the end of Horizon: Zero Dawn mean?

What did we think of Horizon?

SPOILER WARNING: We’re talking about the ending of Horizon: Zero Dawn. The ending. So obviously there will be major spoilers. Just sayin’. 

*Takes deep breath* So. At the end of Horizon: Zero Dawn, there’s a certain post-credits cutscene which some might find frustrating, others intriguing. It’s sure to cause debate amongst those who complete the main story mission, as it changes how you’ll see the overarching plot. 

The big shocker is that it shows Aloy didn’t in fact kill Hades completely. After being poked about by some curious citizens the entity jumps out of the core and speeds across the sky, off to god knows where. Although we do know where it goes. Atop a bare rock in the middle of nowhere, a familiar figure holds up a lamp-like canister, ready to catch Hades. It’s Sylens. Yes, honestly: the man who helped you find the master override for Hades in the first place, who saved your life from the arena in Sunfall, who has been tracking your move and guiding you through the ruins of the old world for most of the game. He has more to ‘discuss’ with the AI set on destruction, and - more importantly - wants to know about its ‘masters’. Sounds like someone (or something) woke Hades up. But why? 

The hint that a sequel is on the cards is fairly strong. Plus, frankly, I’m itching for the chance to fight a gigantic Metal Devil.