Khonsu (also called Khons and Khensu) is the Egyptian god of the moon, time, and youth.
When the goddess Nut needed to create extra days to have her children, she challenged Khonsu to a game of senet. Eventually, Nut won enough moonlight to create five more days and was able to give birth to her children despite Ra's attempt to stop her.
According to Khonsu, Bes wanted to spend more time with Bast, his secret crush, so he wagered a few feet of his height. He lost, which might explain why he is a dwarf god. However, Bes denies this is true.
Carter and Sadie needed to reverse time by 3 hours to continue passing through the Houses of the Night so Khonsu was invited by Osiris to give them the time they needed. But, as Khonsu explained, he can't simply give them time since doing so would be an act of chaos. So the only way Carter, Sadie, and Bes can receive his help is to gamble with him, betting their three rens against three hours of moonlight.
The Kanes won in the end, but Bes' ren was devoured in the process. Even as their quest went on, Sadie and Carter continued to express their rage towards Khonsu. Shortly after their game, Carter lunges at him before he disappears. Sadie unleashes her fury on a group of demons by turning them into Khonsu bobble heads. He makes a brief appearance when Ra returns to his throne and Sadie feels the urge to punch him.
Khonsu appears before Carter as he demands gods to fight by his side. He then fights against Apophis.
Khonsu states that he has adapted completely to the modern world, but in reality he's quite a scoundrel. In Ancient Egyptian times, he was known for helping the pharaoh slay any gods that were bothering him. Khonsu is always ready and willing to devour the souls of anyone, and was eager to take the ren of either Carter, Sadie, or Bes. He acts like a scam artist and adores gambling, as he was actually making bets on the outcome of the Kane's quest to bring Ra back.
He doesn't really care about whether or not Chaos wins because, as he explains, change comes in phases, and he even feels sorry for Ra for having to stick with such a strict schedule. Khonsu also reasons that Apophis will leave the moon alone since the snake monster is only really interested in the sun. It's quite apparent that he does find joy in devouring the rens of others, but he doesn't seem to catch onto people not liking him. He continuously calls Bes "Old Buddy" and he stays very relaxed around Carter and Sadie even after destroying their friend.
In the duat, Khonsu appears as a glamorous young man dressed mostly in silver. He wears a silver Italian-tailored suit as well as several platinum chains around his neck and one large crescent moon amulet. He has rings on all of his fingers and a silver Rolex which he uses to reverse time. His hair is black and worn in an ancient Egyptian sidelock (worn by ancient Egyptian youth). He usually comes off as charismatic and open, but his silver eyes remain cold and threatening.
Khonsu is said to not only have the power and ability to control moonlight, but also lengthen or shorten the lives of mortals. He can also have the ability to control time, and even gods can be affected by his power.
Bes: According to Khonsu, Bes once gambled with him to spend more time with Bast, and wagered a few feet of his height. He obviously lost (which is why he is so short), and as a result considers Khonsu a scam artist. Khonsu does not see things this way and acts like he and Bes are good friends.
Carter and Sadie Kane: After Khonsu took Bes's ren and his body (which was not part of the deal that the children made with him), they hold him in the utmost contempt. Sadie tells him that she hates him and calls him names, and Carter even tries to attack him. At the Throne Room of the Gods later on, Khonsu is seen and Sadie wishes to herself that she could punch him. He seems to think of the children as more of a source of entertainment.