Demonicon is a decent action RPG, unfortunately weighed down by some obvious flaws.
The best part of Demonicon is the story. It starts off a bit slow, with the player character Cairon's sister Calandra being forced into an arranged marriage to a wealthy noble. But towards the end of the first chapter things get much more interesting as you learn about an ancient demonic ritual where seven children were given dark magic powers.
Sadly the story is undermined a little by the dialogue, which is at times poorly written. Sometimes the dialogue choices don't flow like a natural conversation and several attempts at humour just end up being wierd. Voice acting is also low quality. Calandra is okay, but Cairon just sounds bored most of the time, and the supporting characters are poor.
Combat is fast paced and can be entertaining, especially when you unlock a few abilities. Most of the time you are alone, controlling Cairon in 3rd person, against waves of between 6 and 10 enemies at a time. You have melee attacks with either blades or blunt weapons, special melee power attacks, throwing knives for ranged attacks and four magic spells - freeze (mainly used against a single target), fire (radial damage perfect for when surrounded by multiple enemies), speed/damage buff and poison (which I didn't try because I put all my points into upgrading the other three). Its like a lower quality version of the Witcher.
There is some variety in enemies - Human rogues, mages and warriors, spiders, lizards, fire demons - enough to make me change up my tactics based on their weaknesses and abilities.
The level up system is based on a German pen and paper ruleset called Dark Eye, which I've also seen in Drakensang. You don't gain levels as such, but every fight, quest and many non-combat actions gives ability points which can increase stats (strength, constitution, etc), melee power attacks, non-combat skills (crafting, lock picking, etc) and magic. You can spend the points at any time as long as you have enough. I like the system because it feels like there is alot of freedom to build Cairon to suit your playing style.
Level design is mostly linear with some small side paths to find extra loot. There is more freedom during quests, many of which give the player a choice how to resolve. The save system is checkpoint only, but most of the time they are quite frequent. Controls are fully rebindable and work nicely with mouse and keyboard.
There are some problems on the technical side. I sometimes noticed some stuttering while running around, and some slight framerate dips during combat. I also crashed to desktop twice on the crafting menu.
Overall I think Demonicon would probably only appeal to dedicated RPG fans. If you can be in a forgiving mood and you've played all the better games, there is some enjoyment to find here. I finished the game in 16 hours, so I wouldn't recommend picking up at full price. I bought it for 75% off, which considering its flaws, seems like a fair price.