Welcome to Act IV, the home of Diablo, and the end of the pre expansion game. Here's the deal, it's pretty easy. You're in Hell. Tyrael is there as well as 2 NPCs whom never talk, but I assume they're some kind of angels, or npcs from the first game (which I never played). Anywho, you fight your way through Hell to Diablo's lair, which is shaped like a pentagram. You open the 5 seals (each time you unlock one you're flooded by badass npcs) and then Diablo pops up and you fight for ever (at least, you do as a dual wield assasin with low resists. Other players don't have the troubles that I do with this Diablo guy). When I took him on he WASTED me. I had almost no resists and I couldn't hit him, even though my atk said I had like a 70% chance of hitting, it was more like 20%. Took me a good 40 mins to kill him as I remember...and I used all my rejuvination potions, and health potions, and even all my cash buying more health potions.
Here's the bloody mess after defeating one of the stronger monsters
on the way to Diablo:
They had some fun with the names of the places you pass through on your
way to Diablo. This part was called the Plains of Dispair.
You know, I hear the Plains of Dispair are lovely this time of year...
And here we go, the big guy himself. Like I said, took me a good
40 minutes. I just wasn't developed as a character, or ready as a
player, to face Diablo yet. But I won anyway. I took this picture
at the very begining of our encounter:
And here I am, 40 minutes later, FINALLY killing him: