To say the truth, at first I only played Spiral Knights for the Team Fortress 2 hat, but after some gameplay I found out that the game was fun!
It has literally been the only game I've played since I discovered it.
The game is still somewhat in a beta. Many times every month new items are added, bugs are fixed, monsters are altered, and so on.
The story starts as such:
The Spiral Knights crash onto a planet with their spaceship, The Skylark, which is damaged beyond repair. On this hostile world they must survive. Deep below their new home, Haven, is a place called The Clockworks. Alot of zones connected to elevators, that shift (in real time). Only the most skilled players will ever see all zones.
To keep The Clockworks working they must enter them and bring crystals back up. The crystals produce large amounts of energy, which The Spiral Knights need.
In these Clockworks many monsters have homes. They are both Jelly Cubes, Machines, and even undead or ghosts.
To go into the clockworks you need Energy. You start with 100 Mist Energy and 0 Crystal Energy. Mist Energy regenerates 100 energy over 24 hours. Crystal Energy must be bought with real money, or with Crowns, the currency in this game. The maximal Mist Energy is 100, while you can get unlimited Crystal Energy.
It takes 10 energy to go one depth (level) down into the clockworks, and so far there's a total of 29 depths.
Energy is also used to craft weapons. A star 2 (of 5) weapon uses 50 energy. A star 3 uses 200 energy.
When you craft weapons, they have a 25% chance to give an extra attribute, like take less damage, deal more, charge faster, better resistance, etc.
The best weapons are also crafted.
All weapons can be Charged. Charged weapons deal extra damage, and may have extra attributes. The stun gun, wheb charged, can stun the enemy, while other weapons may send the enemies flying backwards. Charging takes around 4 seconds, but faster with some weapons.
Guns deal less damage than swords, but are ranged. Better shields can take more damage when shielding yourself (default X button). Better armor and helmets can give you more HP when in dungeons, better resistances to, for example, frost, shock or fire, or just look cool.
This game is probably one of the funniest games I've ever played. The graphics aren't the best, but they definetally fit to the game. You can customize your character in a million ways, and it is possible to join guilds, and play with your friends down in the Clockworks.
The biggest minus is the Energy function. For new players, or people that do not want to pay, it is really hard to have fun for longer time. A 100 energy is used in about an hour, and even faster if you craft weapons.
Overall the game is GREAT! It is Free-to-Play, and you don't really need to buy anything, because the Packs give around 750-7500 crystal energy, but only some weak weapons. You don't have a handicap if you don't wanna buy anything (yet!) which is awesome.
Thinking everything through I'd give it 9.5 (10 if they removed Energy limit, or if they created some Mist Tank that could store energy, when you don't use it after reaching 100 energy.)