Ser Clayton is a short burly man with a balding head and a mouthful of broken brown teeth. He has a deep voice. Clayton is considered a crony and the strong right hand of Ser Godry Farring. He is cruel and enjoys torturing, especially women, and it is rumored his love for the Lord of Light is only love of human sacrifice. Despite his cruelty, he's considered brave and loyal.
Clayton hails from Flea Bottom, in King's Landing. According to Ser Justin Massey, on Dragonstone Clayton would gamble with the torturers and lend them a hand in the questioning of prisoners, especially if the prisoner were a young woman.
When Stannis declares himself the rightful King of the Seven Kingdoms, Clayton supports him and the new official religion of Dragonstone, the faith of R'hllor. It's unknwon if he took part in Stannis' campaign before his defeat at the Blackwater, or just remained at Dragonstone, serving under Queen Selyse Florent.
After the death of King Joffrey Baratheon, Stannis, now calling himself King of Westeros, goes to the Wall and Clayton is among the knight who went north with him.
Stannis defeats and captures Mance Rayder and many other wildlings. At Castle Black he sends ravens to the noble houses of the North, commanding them to support him and accept him as their king, but he only gets silence or letters of refusal, while others are fighting for the Boltons, and only Arnolf Karstark joins his cause. Clayton states that Houses Hornwood, Cerwyn, Tallhart, Ryswell and Dustin are all traitors and lapdogs of the Lannisters. When Stannis dismisses his men during a meeting with Jon Snow, Clayton drains his cup dry and mutters something to Lord Harwood Fell that makes him laugh. Jon Snow considers Clayton an upjumped hedge knight "as crude as he was strong".
Clayton is among those who march with Stannis out of Castle Black. They go the Northern Mountains where they get the support of the Northern Mountain Clans, then they march on Deepwood Motte, where they defeat the Ironmen, liberate the castle, and capture Princess Asha Greyjoy and all her surviving friends. During the fight they are joined from the sea by House Mormont, who had previously refused Stannis. For this, Stannis and his men gain the support of many northern houses, who join their host. Stannis gives Deepwood Motte back to the Glovers, they remain in the castle for a short while, before marching on Winterfell.
During the march in the wolfswood, Stannis and his host are taken by a sudden heavy snow blizzard, but this doesn't stop the king from keep marching. After many days, and deaths of men and horses, Stannis' s host make camp in an abandoned crofter's village. Suggs agrees with Ser Godry Farring they should burn someone to appease R'hllor and end the blizzard, but Stannis refuses and tells them to pray harder. Asha Greyjoy believes it is her whom Suggs wants to burn. Asha does not like Clayton; to her he seems simply cruel. Clayton insults and goads Asha constantly. She has seen him at the nightfires, watching, his lips parted and his eyes avid. She concludes to herself that it is not the god Suggs loves, it is the flames.
The army remains at crofter's village for weeks, until they end up starving in the snow, and the blizzard doesn't seem to end. Only the northmen in the camp are resisting well, being used to this weather, while Stannis' men from the crownlands, the stormlands, and the Reach are dying of sickness or starving. Stannis, being a loner, remains isolated from the rest of his men and shuts himself in the abandoned tower of the village. Later 4 men of House Peasebury are caught committing cannibalism and they are burned alive as a sacrifice to R’hllor, except the serjeant, who throws insults to goad Clayton into killing him with a knife. Clayton never says a word, one quick slash opened the serjeant’s throat, sending a wash of blood down his chest. Clayton watches amused the men being burned alive, in the hope of stopping the snow blizzard and Stannis joins his men to watch the sacrifice.
Later when Clayton finds Asha alone looking at the burned corpses of the sacrificed men he insults her. She thinks to herself that Suggs is worse than Middle Liddle. She reminds Clayton that Stannis gelds men for rape and he laughs saying he would sooner see her burn.
Suddenly they hear riders. Clayton rips his longsword from its scabbard and tells her to run and warn the king, as he assumes it is Roose Bolton’s host upon them. Asha notes that a brute he might be but Suggs does not lack courage. However, the riders turn out to be Tycho Nestoris of the Iron Bank of Braavos and his escort, some of which are Asha’s ironborn men.
Stannis still remains secluded in his tower, preparing to attack the Boltons. Tycho Nestoris brings him a group of men of Mors Umber with the freed ironmen from Deepwood Motte and the captive Theon Greyjoy with Arya Stark (actually Jeyne Poole), both fled from Winterfell. Theon is put in chains, while Stannis learns from a message from Jon Snow about Arnolf Karstark being in league with the Boltons and plotting to betray Stannis outside Winterfell. Clayton is present along with Ser Richard Horpe, Ser Godry Farring, and the prisoner Theon when Stannis interrogates and intimidates Maester Tybald about his loyalties. Stannis has Clayton threaten violence on the maester to make Tybald tell him everything. After the maester's confession Stannis has him, Arnolf, Arthor, and the other Karstarks with their men arrested. He promises that all of them will die.