I'm a little late to the party on this one. As a promotional thing for Sundered, the devs gave out their earlier game (Jotun) for free on Steam. I played Jotun, and it was so underwhelming that I avoided Sundered entirely; perhaps it wasn't the best promotion strategy? Regardless, I picked up Sundered during the Steam sales. It's a Lovecraft-themed metroidvania with some rogue-like elements, so I figured it would be difficult to screw up that formula.
The first thing one notices about the game is the original art style and atmosphere. There are many Lovecraft-inspired games, but I haven't seen any of them capture the surreal cosmic horror aspect so well, apart from Bloodborne. All of the environments are beautifully hand-drawn, and all of the monsters and bosses are frame-by-frame animated and coloured in a beautiful manner reminiscent of Akira or Ghost in the Shell. The game is gorgeous, but they also somehow managed to retain this beauty and visual coherence within the randomly-generated levels. There are 3 main zones in the game, and each one has its own individual style, atmosphere, monsters, bosses, music and unique platforming challenges.

The game is pretty, but my initial fear was that there was too much focus on the visuals, and the gameplay would suffer (possibly the downfall of Jotun). Surprisingly, the gameplay and movement are really well-designed and silky smooth. I could draw a lot of comparisons to Dead Cells, and after playing a lot of it, I found that the movement felt much more free and acrobatic in Sundered. There's a giant skill tree with unlockable skills, and perks that one may equip, in a pretty standard metroidvania manner. Double-jump, grapple hook and other skills allow one to access deeper into the world and reach tougher areas and bosses. Though I think the crowning achievement of this game is the innovative map-generation technique, which sets it far apart from games like Spelunky or Dead Cells.
Every time you die in Sundered, the map re-shuffles and you're presented with an (almost) entirely new set of challenges, sections to navigate, hidden treasures and so on. However, instead of killing off your progress, you get to keep all your currency/souls and all your skills, so you become more powerful through each death. Furthermore, the map isn't entirely random. Key areas (like boss arenas, story nodes, central landmarks and passageways between zones) remain in the same locations; it's one the spaces inbetween which are shuffled. I thought this was really clever. It makes the world seem always familiar but never boring: you're never lost, you usually have an objective in mind, but it's never repetitive to get from A to B because there are always re-shuffled challenges during the inbetween sections.

One might raise a complaint about the lack of enemy varieties in the game: there are 3 main areas in the game, each has maybe 4 enemies, meaning only around 12 "mobs" in the game (not including bosses). But I think the game makes up for this with the attention to detail of each enemy with their animations and individual behaviour. If I had to raise a complaint about the game, it would be the enemy spam. Unlike in metroidvanias, enemies aren't actually placed throughout the level: they spawn in on a timer. Every couple minutes a gong will sound and a wave of enemies appear from offscreen. It usually works quite well, except for some flying enemies which can move through walls, trolling you with projectile attacks from offscreen. Other times literally hundreds of enemies will spawn at once which isn't a fun mechanic (especially in the early-game), removing all skill from the experience: you're basically just spamming dodge or attack buttons or running away. You can't really do much when you're being attacked from all directions. I think it would have been better gameplay if they introduced stronger enemies instead, allowing you to actually dodge their attacks.

Sundered was much better than I expected. As you progress through the game you really feel so much more powerful. You start off as a weakling, terrified of certain areas, but by the end you're smashing your way through the most fearsome enemies and bosses with crazy Cthulhu powers, it gives a really satisfying sense of progression. Once you unlock the cannon, even the spammed enemies aren't too much of an issue and it's actually satisfying to slice through hordes of enemies, Dynasty Warriors-style in the late-game. This game (especially early on) is very difficult and punishing and you'll die a lot, but that's part of the experience. I've drawn a lot of comparisons here, but this game feels quite unique, and it's worth experiencing even just to witness the incredible animations and the unique interpretation of cosmic horror. If you're a Lovecraft fan, or if you enjoyed Hollow Knight or Dead Cells then I think you should definitely check out this game. :)