Diablo quest chain is still in progress
it will be raid and party bosses
you will get quest from deckard cain leading you to kill raid bosses, diablo, mephisto, baal and bringing their soulstones back to cain, you will later in the quest line visit tristram, wirt, griswold, duriel, andariel, cow king and secret cow level (and maybe also see tyrael fight izual (and maybe join in the fight MAYBE JUST MAYBE))
this quest chain will be available for all and secret cow level will be a portal in the mall for all on server to use for 1 day IRL time, then it will close again for all.... this place will have lots of more exp and loot and easier to get levels compared to rest... sort of a event... but getting it open will be a achievement itself and will be wellknown who has opened the portal since this person will recieve aditional rewards... inside this area you will also have 1 more optional quest AND raid boss, these will be even harder and wield ALLOT of great items with much special features