Surprisingly, the PCs wiped the floor with poor Zhengi. (well, it took a few dozen rounds.)
On the random Abyss encounter table, I rolled Lloth. (and priestess cohorts) When the PCs saw me pulling out D&DG, their jaws hit the floor. Ironic, because Lloth took a dirt nap after 5 rounds.
The city of Liches, however, (since the imp did trick them to going there

) was the only place exempt from their abyssal killing spree. (The party was not keen on battling 6 demiliches and 6 death knights. I think they were confident with killing the liches though...) One of the PCs, who had started a chain of Magic Item stores "Curious Goods" found it funny that with a bit of diplomacy, he set up a shop IN the city of Liches.
Orcus' castle was little challenge for the players (Except for the bridge, which killed the fighter) but the puzzles infuriated them.

(In a good way)
By the time they reached Orcus, I had him use his trump card: He had managed to locate a Hecatoncheires to use as his General as he conquored the planes. (and Arming it with 100 +5 Githyanki Vorpal Blades no less!) The battle went poorly for the PCs. (The Arcane Archer thought he was safe in a Prismatic Sphere. When it just waltzed through and killed him he was quite surprised.) The PCs killed it by first rusting its swords, (Draconic Wildshape + Rust Dragon) then fleeing back across the land while summoning as many Angels as they could. about 30 Greater Planar Ally spells later, they had enough Solars to rush the thing and kill it in Melee.
In the end, Orcus (100hd Infernal) got massacred and the party then took the Wand of Orcus straight to Tiamat, whom they killed in one round thanks to 3 (2 of which were demi-gods by then) mages casting very much empowered Horrid Wiltings. (Though because of this, they had too search long and hard to find any of her blood)
Good times

Chronicle seems so far off

but Grimoire and Bestiary #2 seem more important.