Take a top down Diablo-style game but as an MMO, add excellent Korean action combat, tons of activities in PvE and PvP including dungeons, Monster Hunter like fights, sailing and everything casual and hardcore you can think of, add great visuals despite fairly low requirements, and you get Lost Ark.I give up... what's Lost Ark and why's everyone nuts about it?
Oh and it's F2P.
But it's not very anime though, it's your regular Korean artstyle which is a weird idealized realistic style. Environments look fantastic, characters are a bit weird. But it does have good customization (for your face anyway, your body is pretty much fixed), and for once I managed to make characters of very different ethnicities without problem, it's not just a skin tone swap.