Nice combination, I'm working on something similar atm due to start in January so I suspect my research will have been pretty much on parallel lines to your own. I decided to put the Korvosa and Lady's Light material to one side tho' unless the party are determined to follow up on the links to the Brotherhood of the 7, mostly because I'm too lazy to adjust all the encounters for the different party level. Instead I'm going with Asylum Stone and Doomsday Door which seem to dovetail more easily without level adjustments and help the party level up at the right speed to follow a medium advancement(I figure whilst they're RotRL'ing the Pathfinders can despatch some other adventurers to the Lady's Light and they can be told all about it when they return as mighty heroes from RotRL parts 5 & 6).
Anyway in answer to your question there's very little material on the Runelord of Lust CotCT, book 6: Crown of Fangs (pp.20-26, 36, 46-48, 56-57 & 60-61) is pretty much it... In particular the Shoanti have forgotten why the Great Pyramid of Lust was a place of evil... they just vaguely remember that it was/is. Page 56 of the Guide to Korvosa also has a tiny amount of material on this which boils down to (from the Shoanti perspective) "There's something evil down there!" and (from a magic users perspective) enchanter wizards are surprisingly common at the magical academy there.
The Shoanti protected it for a time but swiftly forgot why (which given the enchantment angle is probably understandable...), although Shamen and witches (a Shoanti witch sounds terrifying btw... awesome concept!) remember that something evil resided there. The arrival of the settlers who founded Korvosa largely drove the Shoanti from the region so no Shoanti guardians remain. Some of this conflict is expanded on in CotCT, book 4: A History of Ashes which also contains a chapter on the Shoanti legends about the Runelords (from a mythologised in character perspective that might be useful to your player), the material in this book also references a Shoanti plan that might be worth a read and could potentially be tied in to your story...
Obviously Inner Sea Magic includes brief material on what level/class the Runelords were alongside a few pages on their magic. Given that Sorshen was one of only 2 "original" runelords I'd expect her to be a bit more powerful than Karzoug. I assume you've got the material regarding the 7 swords of sin - tools of the Runelords champions? If you're using a "multi-runelord" approach these swords will have been locating wielders and heading to their respective owners domains...(perhaps a Shoanti Shaman is trying to stop that from happening in this case which could be used to replace the Shoanti encounter in the early CotCT adventures?) more material can be found at http://www.pathfindercommunity.net/magic-items/artifacts/major-artifacts/se ven-swords-of-sin
As an aside there is a range of additional material around which supports the multi-runelord approach. In particular the Pathfinder society scenarios covered an arc on the rise of the Runelord of Sloth (the finale is summarised here: http://paizo.com/products/btpy8we6?Pathfinder-Society-Scenario-4-26-The-Wak ing-Rune There were also several other adventures involved forming part of that years run). There's also a fair amount of material for the Runelord of Gluttony dotted about which you've probably located.
Hope that's of some assistance to you.