Hero Siege Acts 7-9 Walkthrough: The Rift, Valhalla and the Abyssal Realm

How Do Acts 7-9 Differ From Everything Before Them?

Nothing in the final third of Hero Siege’s campaign is new information — Acts 7 through 9 exist to find out whether you actually learned it. The earlier acts alternated lessons with mercy; these three assume a finished build, hold that standard across longer maps, and end with the most consequential fight in the game.

Act 9 is intentionally listed differently: it is a single-zone finale rather than a landmark chain, which fits its job — one arena, one exam.

What Does Mevius Still Test in The Rift?

Act 7 leaves the planet behind — Deep Space out through the Event Horizon, the Black Hole and the Parallel Dimension to the Subconscious Mind — and Mevius waits at the end with the campaign’s cleanest endurance test. The fight asks the two questions late-campaign builds live or die by: can you keep dealing damage for a full phase without a rescue cooldown, and can you reposition without losing your rotation.

The Rift is also a piece of Hero Siege history. For a stretch of the game’s life, reaching this fight required owning the Wrath of Mevius DLC; that gate was later removed. And older community guides carry a second outdated claim — that defeating Mevius at 7-5 is what unlocks the next difficulty. That was true of a shorter, earlier version of the campaign; Season 10 runs nine acts, and the difficulty ladder’s hinge now sits at Act 9’s finale.

Why Is Odin the Gatekeeper to Act 9?

Act 8’s Gates of Valhalla runs from the Forest of the Slain through the Flooded Plains, Forgotten Caves and the Camp of Souls to Helheim, and Odin closes it. His kill is not symbolic: Act 9 does not open at all until Odin falls. There is no shortcut, no crafted key, no side route — every path to the Abyssal Realm starts from a Valhalla clear, which makes Act 8 the practical checkpoint of the final third. If Act 9 is locked, the answer is Act 8, not a build tweak.

How Does Cthulhu Unlock the Rest of the Game?

Cthulhu is the campaign’s last fight and its most load-bearing repeat kill. The chain, as documented on his page: clear Act 9 on Normal and Nightmare unlocks; defeat him again on Nightmare and Hell opens. From there the ladder follows its fixed rule — each tier unlocks by finishing the one before it — which is how the road to Inferno runs through the same finale. The difficulty guide covers what each tier changes.

That structure is worth internalizing, because it means your first Cthulhu kills are unlocks, not farming. The loot conversation starts after the ladder is open.

Where Do You Go Once Act 9 Falls?

The campaign hands you to the endgame’s two tracks. The first is the wormhole push — the scaling loop where builds get stress-tested for real. The second is the Uber roster: the classic trio plus the Season 10 newcomers, which sit above the campaign in both difficulty and reward. Running all nine acts again at the top tier is its own milestone — the Inferno acts guide covers that route and the community benchmark around it.

Acts 7-9 FAQ

Is Odin the final boss of the campaign? No. Odin is Act 8’s boss and the prerequisite for Act 9 — the finale belongs to Cthulhu in the Abyssal Realm.

Why do older guides say Mevius unlocks the next difficulty? Patch drift. The claim comes from a shorter, earlier campaign; since Season 10 expanded the game to nine acts plus Inferno, the difficulty hinges run through Act 9’s finale instead. Check any guide’s date before following its unlock advice.

Can you run Acts 7-9 in co-op? Yes — the late campaign supports both local split-screen and online rooms, and the hardcore and co-op guide covers how the lobbies and difficulty settings work. Co-op does not skip the Odin prerequisite or the difficulty chain.