So anyway it was time to take on the Ancients. Before setting them loose, we paused to take a moment to plan out a strategy for the battle. It was decided that we would try to lure the three Ancients in three different directions, isolating them so that they could be easily taken out. We popped the seal (or whatever it is) and the Ancients indeed scattered. Success! 
Of course, the corollary of splitting up the Ancients meant that we Rogues were split up too, but that proved not to be a major obstacle. Here, Sirian and I have Madawc cornered and are smacking him around with our melee weapons. I don't even know what his aura was, but separated from the others, it doesn't appear to be doing much of anything. Madawc went down in fairly short order.
Now on to Korlic. You can tell he's Spectral Hit by the fact that he poisoned Svava, heh. From left to right, the Rogues beating on him are Sirian, Jaffa, Alan, and Svava (me). Cy is down at the bottom with the shield. I know all this for certain because I have a picture of everyone's character gear with their names from this point in time. Korlic was tougher than Madawc, but still not sturdy enough to stand up to this combination of Rogues.
And everyone is together for the final fight against Talic. Uh, now that it's been stripped of its healing capacity, Teleportation is not the scariest boss ability. And while Talic may have a nifty sword there, the Rogues have swords of their own to play with too. It didn't take long to send the final Ancient down to the deck, or, erm, turn him back into a statue.
The Worldstone Keep had more nasty combinations of monsters, almost as bad as the ones in the Halls of Pain:
This was a boss breeding monster; there were a ton of them on this level of the keep. I believe that we had more Hierophants/Zealots again, and the third monster on the level I can't remember. Something bad though. (Dathon later reminded me that it was beetles - so it was indeed something bad!) We had the staircase trapped on one of these levels and completely lost the area, but were able to re-establish ourselves from a portal and clear the level from there, with the multiple boss packs around the stairs being the last enemies to fall. Lots of tough fighting again, but doable with everyone working together.
Here's Lister again, and it looks like he has a Conviction aura as his special ability. Although the seal bosses should have been more difficult here in Nightmare, and they did take a long time to take down, I believe we actually fared a bit better than we had in Normal. By now everyone was used to having to run from tough bosses, using tactics to split up boss packs, and so on. We had gone through Normal quite fast, and the threat level had been relatively low, so we didn't really know what we were doing at that time. By the end of Nightmare though, all of the Rogues had gotten to know their characters much better, and we had vastly improved as a team. I think it really showed in how we managed tough fights like this.
Baal was the only foe left to defeat in Nightmare, and he's really taking a pounding here. I expected a difficult battle against Baal, but he really let me down. I believe that the Rogues have actually managed to get the big guy stunlocked here; either that, or his AI programming doesn't know how to respond to being hit from multiple sides at the same time. In any case, Baal basically stood rooted in one spot while the Rogues emptied thousands of arrows into him. What a fight! But a victory is a victory, and Baal went down for the count!
The first session of Nightmare had been October 25, 2004 (our seventh session overall). Baal went down (I believe) for the first time on January 10, 2005; I have no clue what game session it was (we had played a lot). From the dates involved, it should be clear that Nightmare took a lot longer than Normal! We ran the Ancients and Baal again shortly thereafter to get Hawkmoon caught up into Hell difficulty, with things going much the same. Baal again stood in place without doing much of anything. Now take a look at the proud Rogues who had just completed Nightmare, reveling in their new titles:
If we had this difficult a struggle getting through Nightmare, what is Hell going to be like? There were clearly many difficult roads for the Rogues still to travel, but they had only three words for Diablo and his ilk: Bring It On! 
