Gil Greyling is a Blackguard and the older brother of Gavin Greyling, also a Blackguard. Of the pair, Gil is regarded as more intelligent, while Gavin is regarded as more handsome.
After Prism Gavin Guile accidentally threw Ana Jorvis off the balcony of his chambers, Gil and Gavin Greyling covered for him by swearing to Ironfist, the White, and the Spectrum the same story: that Ana had snuck into Gavin's chambers and attempted to seduce him as he slept. Gavin, not being able to see who it was in the dark, thought that Ana was either Karris White Oak, whom Gavin had just reconciled with, or else Gavin's room slave Marissia. Just as Gavin realized that Ana was neither of the women, Karris entered the room and, upon seeing what was going on, stormed back out. Gavin ran after her, bent on explaining and apologizing, but was stopped by Karris' fellow Blackguards. Upon returning to his chambers, Ana requested that Gavin return to their lovemaking, deriding Karris in the process as being old, ugly, and boring (three things that Karris is not.) In a rage, Gavin threw her onto the balcony and began screaming at her that Karris was the woman he loved. Distraught and fearful, Ana leapt from the balcony to her death. All of this is true, except for the part about Ana leaping. In truth, when Gavin threw her, she hit the balcony railing and flipped over it, sending her plummeting over the side. Despite the fact that her death was an accident, Gavin would almost certainly have been impeached from his office as Prism were it not for the Greyling brothers covering him.
After the official investigation had concluded, Arys Greenveil, the sub-red of the Spectrum and Ana's aunt, hired the most beautiful courtesan available to get Gil drunk, seduce him, and extract the truth of the events from him. To his credit, Gil's story did not change even while heavily intoxicated and under the influence of the courtesan's charms.