hmm, oh, well since other people responded, I'll clue ya in.
http://s4.en.alaplaya.net/
S4 League ...er... yeah, don't even try to guess the 4 S's, but it basically means..: Stylish Shooting eSper Sport League.
Its an MOTPS, Multiplayer Online Third Person Shooter. I wouldnt call it Massive, since its really more like a chat hub with Arena Matches listed. It has Two modes, Death Match, where two teams of six compete for kills, and Touchdown, where two teams of six try to rush the center of a map for a ball, and then take it to their opponent's home goal. There was a third mode recently added called Chaser, I havent gotten to try it yet, but I believe its a whole team versus one person for something.
Anyway, each person can fight with 3 weapons, ranged, melee, and special- like turrets, and one special skill, from things like wings, a "zelda-esque" hookshot, or even the ability to erect walls to keep opponents from being able to use a certain path.
http://www.youtube.com/watch?v=pwZKKwcTnJE
check that out or some other vids.
*EDIT*
as for the difficulty, as you play and win, your level goes up, and you gain access to knew ranks of games, receiving a better license. The low level games are pretty "pick up and play" but by lvl 30, from there on, things start getting brutal, and people play really well. Also, leveling takes quite a while.