This is a new and improved Diablo IV

So, Blizzard could’ve just opened up the DLC area, told you, “Go have fun you little scamp,” and called it a day. But no, they’ve actually taken the opportunity to tweak the basic experience a little. If you’ve been away a while, it’s worth spending a little time getting acquainted. For starters: if you decide to make a new character to try out the Spiritborn class, keep in mind that whether you do the campaign again or jump right into Vessel of Hatred, you still need to clear the Prologue. After that you can exit out and go to the Seasonal mode at your leisure.
Once you do jump in, you’ll notice there are quite a few more options for difficulty as well, with the World Tier system changing from just Worlds I-III to around half a dozen Torment levels, each more hostile than the last. Jewels now get their own tab instead of taking up valuable space in your loot inventory. And there have been tweaks to each existing class’s damage outputs and movesets as well, along with a change in level cap (Paragon system now unlocks at lvl 60). The list goes on, and it’s worth taking an hour or so to get reacquainted before heading out on your quest.