I'd give this game a 9/10:
Overall this game is really fun to play. It's not too easy and has a frustration factor, but the gameplay is good enough to keep you entertained.
You pick your hero and run around the arena killing monsters, which come in 6 waves per stage, the 6th one being a big boss. Some monsters have certain enhancements or special abilities and there are champion versions.
If you keep going you will find relics granting you special abilities to help you out as well as keys that open chests where you get gold to buy stuff or potions or crystals which can be used to unlock stuff.
Sometimes, bigger versions of monsters will drop a bomb or a circling laser thing or a bomb after they die to finish you off when you least expect it. That's annoying sometimes.
You have to avoid certain traps (or use them to your advantage against monsters), for example spike traps or arrow turrets. Sometimes they can be hidden behind a tree or something, so you have to be aware of your surroundings.
There are multiple classes, from swordfighters to rangers to magic types.
You level up by killing monsters and upgrade your skills and your stats (Attack, attack speed, defense, health).
The controls are good with a 360 controller, you can move in any direction while attacking in any other direction you want (only 90° angles though). I have not tried keyboard controls.
There are multiple difficulties and areas, but you have to unlock them first.
Most of the passive skills seem a bit useless at first, it takes quite a few skill points for them to be really useful, while the active skills seem a lot more viable.
For online multiplayer you have to register with some service, but theres also local multiplayer for 2 players, haven't tried that yet, however.
The game crashed twice on me so far, but I was able to pick up where I left off when restarting the game.