Sadly this game was a disappointment this game shows exactly how to not make a metroidvania, but lets begin with the pros.

The first thing everyone will notice is of course the artstyle, the wonderfull hand-drawn assets look wonderfull and you definitely can see the efford the developers put into this.
There are 3 areas with 3 minibosses and 1 big endboss (there is also an endgame
boss for sure ^^).
The endboss of each area is definitely climax of each area with great design in graphics, gamplay and bombastic soundtrack.
While the minibosses are stronger versions of normal mobs some of them with special abilities, so there can be some interresting fights in there, but not so great such as the enboss of each area.

So you can definitely see the potential this game has, but you can also see how this great potential is wasted.
First thing after a view hours you will notice that the world is randomly generated each time you die or reload the game.
The system works a little bit like in shadow warrior 2 you have bigger boxes which stay the same in theire connection, but theire insides is filled with smaler randomly generated boxes with very view places which stay the same everytime.
Some of the reviewers here call it rougelike but in this game this isn't really the case, it even isn't really well done.
The problem is the world feels boring, you can clearly see this wasn't handcrafted and this settles down in sometimes even horrible level design.
Which makes it even more disappointing is the fact that there are only 3 areas, yes they are big but this makes it even more monotonous, so the visual variety is at its minimum.

The enemies are also pretty bad designed the most of them arent even a foe, so the developers decided to throw wave after wave and huge horde after horde at you just to make it artificially hard.
There are times where the screen is filled with ennemie, bullets, explosions etc... so you even cannot see yourself or dodge any attacks, also it doesn't help that unreachable enemies in walls, spawn in spikes or simply offscreen still shoot at you.
This system leads way to often to bs deaths which leads to more runs which leads to more unsatisfying fights which leads to unnecessary frustration.
This game misses the point of an metroidvania like adventure, since great level and enemie design in my opinion are key in this genre.
In sundered i quickly realised that i'm not able to fight every wave (there are even rooms with infinite waves) and that i'm not able to explore every corner like i normaly would, so the exploration breaks down to get the on the map marked abilities and perks and thats it.

This aren't the only porblems in this game espacially on hard difficulty the game requiers you too grind, just because you just feel to weak for the new area, so eather you run away from almost everything or go back and grind. I decided most of the time to run which hits me near the end of the game pretty hard, that i had to grind really long to feel strong enough for the last 2 bosses. This section can be very different based on choices you made in terms to your abilities, so there are alternative bossfights and endings.

This game maybe isn't completly horrible but i can not comprehend the positive reviews here on steam, yes this game looks pretty, but most of the time the areas look boring and repetetive where you spend mostly 80%-90% of the time.
So the few moments where the game shines really doesn't turn the overall impression of disappointment.
The developers also patch it regularly to make it less frustrationg but i believe that that the decisions in gamedesign overall were bad for this game.
They can't change it's core, they maybe can make it more viable but i didn't believe it can turn to an overall good game that i will recomend to my friends anymore.

If you still consider in buying this make it on sale and play it on normal if you want to have at least a little bit of fun with it.