I just won Skilltree about a week ago. It's trash, but you can get a few hours of "fun" out of it if you have no taste.
It has no story, outside of "girl kidnapped, must save her" so being part of the Dark Eye universe is pointless.
The gameplay consists of two elements, the first is "select what you do before the battle, since there is no interaction during the battle, start battle, adjust what you do to counter that specific enemy in the next battle round or next encounter." It's basically rock, paper, scissors where the same enemy type throws the same R/P/S each time you fight them. If the enemy casts a spell on turn 2, then you should use your "interrupts spells and ranged attacks" skill before, etc.
The second gameplay element is grind. The first two "adventures" aren't bad with grinding, the third is horrible.
Each "adventure" consists of a series of encounters (30, 50, and 100) with a boss every 10 levels. If you fail the adventure, either by dying or retreating, you have to start over next time you want to try. Because you get no experience when fighting enemies 10 levels below your current level, eventually you'll be wasting time fighting low level enemies and getting no experience. You still get loot from weak enemies, but the loot is levelled to the enemy, so it'll be essentially worthless.
Once you get to the heavy grind, it basically feels like a clicker game with no idle mode. I quit once I needed to fight about 15-20 enemies before I got any experience and wasn't making any advances in loot to speed things up.
The grind may not be quite as bad if you actually mess with skills, but I couldn't be bothered to write down the skills each enemy used and go through the clumsy system to change my skills to match every single battle. You would think you could quickly and easily drag and drop to add/remove skills from your turn bar, but you can't. You have to click the slot, click the skill (or scroll through the entire skill list), wait for the UI to catch up, then equip.