The Poem of the Seventh Morning is a source of commentary which has been lost, but which gives reference to Talatin's opinion on an opponent s/he fought as a Knight Radiant.
"They changed, even as we fought them. Like shadows they were, that can transform as the flame dances. Never underestimate them because of what you first see."
–Jasnah's note: Purports to be a scrap collected from Talatin, a Radiant of the Order of Stonewards. The source - Guvlow's Incarnate - is generally held as reliable, though this is from a copied fragment of "The Poem of the Seventh Morning," which has been lost.
Complete:This page has sparse information from the books. However, it does contain everything we have on the subject at this time.