Cronous is a free-to-play MMORPG by developer Lizard Interactive. Quest, loot, and kill your way through the game world. While at first this seems like every other MMORPG out there, the part where Cronous is unique is the castle system.
Once in a guild, you and your fellow guilds-members can either construct a castle, or attempt to take-over an existing one. The castle serves as your homebase, and also looks really cool. But be wary, for there is no shortage of guilds who would enjoy un-seating you from your throne and taking your castle for their own.