Lvl 49 Bloody Foothills
Doh stupid Foothills again. I let UltraLow just pass all critters that were busy fighting barbarians, only killing those blocking the way. I socketed the merc's Wall of the Eyeless after having killed Shenk for a PDiamond. His resists improved to 69/39/69/59, which is quite high for a merc at lvl 48. Combined with the MDR of his Vipermagi all the fire attacks in the Frigid Highlands couldn't hurt him at all. Not that I spent too much time their - just rescued the Barbarians and skipped anything else.

Lvl 50 Arreat Plateau
Ultralow activated Vigor to cross the Arreat Plateau as fast as possible. This won't work in the Crytalline Passage anymore - running into a nasty Mood Lord boss pack might be instant death. UltraLow had to kill everything on the way.

Frozenstein (CE spectral hitting LE CI) showed up on the other side of the frozen river (the ice on the river must be quite thin btw), which made him a helpless victim for UltraLow's arrows. The quest reward improved the resists to 75/39/75/-60.

Lvl 51 Nihlathaks Temple
I tried to avoid the critters in the Temple garden running up straight to pindleskin, but he turned out to be FE/LE/CE and I had to TP out before getting surrounded. Ok spent all 4 unused skill points to Redemption and cleared all the Reanimated Horde.

The way down to Halls of Vaught was found pretty quick and Nihlathak is on the first branch. No problems to get rid of the merc this time. Just don't help him when confronted with Ice Spawns and he is dead already. Start lure all critters out of Nihlathak's hide and kill them in a save area, and use Redemption to remove corpses. After Nihlathak is isolated, I tried to finish him off with Kuko but this is quite dangerous because the spawned Ice Spawns are so vulnerable to lightning and fire. I stopped that after UltraLow was being hit by a CE with only 334 (of 1327) life left, and switched to Smite and tried to bring down his life as far as possible. This would be easier with cannot be frozen, but it still worked quite well. With only a sliver on Nihlathaks life bar left, I switched to Kuko to give him the rest - but this turned out to be a mistake: Nihlathak casted an Ice Spawn, some arrows killed the Spawn, and within the same second he triggered an CE, died, and took Ultralow with him to the graveyard.

I must have had a deathwish. I've managed to get more than 10 chars to Guardian without a single loss, and have been waiting for quite a while to suffer my first HC death. And now I feel relieved that it actually happened. It's not a shame to lose a lvl 51 char when soloing hell Nihlathak IMHO ;) - well not if you consider skipping the quest out of discussion.

In fact UltraLow was more or less done once he hit lvl 33 and started using Kuko - the struggle through Nightmare is the part I'm proud of. Ok it would have been interesting to see him fighting the Ancients and Baal, but after that I would have retired him anyway.