Just a little theory about the parshendi-
Thoughts?
-The parshendi once served the Knights Radiant, just as parshmen still serve across the rest of Roshar.
Evidence:
Directly from book:
• They seem reluctant to fight those who may be Knights Radiant- See mainly the tower battle, where on three occasions, (After Kaladin pulls in the arrows, after he jumps the chasm, and when he saves Dalinar,) - the most obvious displays of power- the parshendi leave on the first, most leave on the second, and none attack him despite his dishonourable conduct on the third. The reluctance of the parshendi shardbearers to attack may also be linked in some way, particularly his words to Dalinar on the tower.
• The honourable battlefield ethic mentioned by Kaladin, and observed by Dalinar, throughout the book.
• This is a possible explanation for where they got the ornate weapons, shards and soulcasters they posses.
• The area (Natanatan) of Roshar that they live in has associations with Urithiru, the home of the Knights Radiant. wrong.
• A weak point, but this may lead to a reason for the assassination (Assuming for the moment that they were responsible) - they wanted to put Elhokar (Or possibly Dalinar) on the throne- both seem extremely likely to be potential Knights Radiant.
• EDIT 25/04/2012 - The battlefield ethic again- maybe they picked the majority of it up from watching the Knights practicing- I'm guessing that would have leaned towards small group/pair tactics, due to the Knight's small numbers?
Fits with other theories/ Q&A answers:
• Another weak point, but the reason they treated Szeth as tool to be used and discarded- it has been stated (I believe) that his powers are from some source other than being a Knight, and so they might view that negatively.
Note that this does not exclude them, along with the rest of the parshmen from being the voidbringers- 4,500 years is a long time- they may only have served the Knights radiant since the last desolation, or possibly between desolations. This is a point that I find hard to reconcile, however.