MegaTen is a FREE MMORPG made by Aeriagames. You can be either a warrior, mage or gunner and each has many different things they can decide to be better at. (For example Destruction Dash-mage and enchancer)
You also have a demon with you that yuo convince to follow you. It will do anything you tell it to and you can even control it by just pressing "tab". You can then fusion two demons together to get a completely new one (and most likely alot better) acquiring skills from BOTH the previous ones.
There are promos almost all the time and events where you get to meet GMs daily and you can even meet them in Babel from time to time to chat with them. Really good game
Aeriagames commercial: http://www.youtube.com/watch?gl=JP&hl=ja&v=1kqbuSDh3Gc
MegaTen link: Shin Megami Tensei: Imagine (MegaTen)