Stellaris: Leviathans Story Pack is a substantial, reasonably priced piece of DLC that no fan of the game will want to miss. It doesn't perfectly capitalize on every opportunity, and isn't perfectly balanced, but it's still a no-brainer for fans of the game.
In the end, HYPER DEMON is a fabulous evolution over the core concept of Sorath's previous game, but it won't be for everyone. The high level of difficulty and demand for skillful play, in addition to the slightly higher price tag of $15 USD, will keep many players away. Others will balk at a game that has only one singular mode to work through, and no amount of leaderboards, interactive tutorials, or its meaty replay and clip feature are likely to make much of a difference. But for HYPER DEMON's target audience, there's really nothing else out there that scratches the same itch, and it's balanced with every bit of the innovation, artistry, and design - to say nothing of the knife-edge precision - that made Devil Daggers such an underrated classic.
Ultimately, Saturnalia is hard to call a must-play horror game, as it's likely to be polarizing both in terms of its presentation and its mechanics. A slower pace, somewhat minimalist gameplay, and mystery-laden narrative style will keep it from being everyone's cup of tea. Yet fans of exploration looking for a beautiful, atmospheric mystery (with just a handful of things that lurk in the dark) will find that Saturnalia is a wholly unique adventure that's well worth taking.