Realm of the Mad God

Oh man, this is truly a cool game! Realm of the Mad God is a fantasy MMO with nice retro 8-bit graphics (looks like they're done by Oryx). The game is heavily focused on fast paced shooter action against hordes of mobs. There's a big focus on co-op play since you share experience by playing together with other players. You can play several different characters, ranging from powerful wizards to tough warriors. The game features a large overworld, many different monsters and items and contrary to most other MMOs it also features PermaDeath (as seen in most roguelikes). When you die you die and there is no way back but to start from level 1 again. Luckily there isn't much grinding in the game.

https://chrome.google.com/webstore/detail/dhjfmaldpppkmjjgkmadddbanpabfflp