Odysseus came across the monsters in his travels, describing the Laistrygonian king's wife as woman of "mountainous proportions." The Laistrygonians ate many of his men and destroyed eleven of his twelve ships by throwing rocks from high cliffs. Odysseus' ship alone survives, as it was hidden in a cove near shore. In The Odyssey, they are described as being more than eight feet tall with wild eyes, and pointy teeth.
Laistrygonian Giants are not birds of North America. In The Ultimate Guide, the Laistrygonians are said to be eight-foot-tall cannibal giants with heavily tattooed arms. They have yellow pointed teeth. Under their clothing is leather armor and that they carry iron clubs.
A group of Laistrygonians manage to infiltrate Percy's school disguised as visitors from Detroit and join a dodgeball game after being recruited by Percy's new bully Matt Sloan. During the game they transformed and attacked with flaming dodgeballs. Through the combined effort of Tyson, Annabeth Chase, and Percy Jackson, all of them were defeated. After Annabeth says the species name, Percy is amazed at how complicated it was, and retorts "Laistry-what? What's that in English?" Annabeth then replies "Canadians."
While using Rachel Elizabeth Dare to help navigate the labyrinth, Percy, Annabeth, and Rachel are all captured by Kelli and a Laistrygonian giant, who marched them into Antaeus' Arena. When Annabeth tried to warn Percy that Antaeus' mother was Gaea (meaning the earth would heal him), the giant placed his hand over her mouth to silence her. It wasn't until Percy blew the Stygian Ice Whistle, calling Mrs. O'Leary, that the giant was knocked aside and the trio escaped.
Two more Laistrygonian giants appeared in Daedalus' Workshop, following Minos and carrying Nico di Angelo in with them. A fight soon broke out, causing Mrs. O'Leary to attack one while another broke a work bench. When the Titan Army erupted from the entrance of the labyrinth inside the magical borders, a dozen Laistrygonian giants lead the charge. While the giants were slowly pushed back by the Apollo cabin archers and Charles Beckendorf's catapults, more monsters came from the entrance. The giants eventually retreated when Grover Underwood released the power of Pan, by using Panic.
A group of Laistrygonians appear on the Princess Andromeda. They manage to hold onto Charles Beckendorf after capturing him. When Kronos had doubts that Beckendorf was captured before planting the explosives, he ordered a giant to open the bag. They did so and several cans of food fell to the ground, scaring the giants (who thought they would explode) and giving Beckendorf the chance to activate the bombs with his free hand, sacrificing himself in the process.
Later when Kronos was getting ready to try and invade New York City again from Aunty Em's Gnome Emporium, Kronos uses his power over time to freeze a Laistrygonian in place, along with his french fries. He unfroze a second later as Kronos' spell wore off quickly. During the battle, Hyperion lead a battalion of Laistrygonians into Central Park, where they attacked many wood nymphs and satyrs. The Hunters of Artemis managed to push them back, with Thalia Grace even calling down a bolt of lightning to turn one to ashes.
Mrs. O'Leary later tossed a Laistrygonian like a frisbee when the demigods of Camp Half-Blood were pushed up to the Empire State Building. Kronos appeared on the battlefield with a dozen Laistrygonians carrying torches to lead the way into the city, but retreated because of the timely arrival of the Party Ponies. Finally, during the Titan Army's last push for the entrance to Olympus, a Laistrygonian ran toward Sally Jackson who was looking in a cop car for something. Right before attacking her, she shot it with a gun salvaged from a police cruiser and the giant fell into Nico's Sword, killing it.
A large group of Laistrygonians were camped outside Frank's family home. In order to make it to the house to save his grandmother, Frank called upon Gray to try and lead them away, but he attacks them instead and cleared a path. Once inside the house, Mars appeared to Frank and explained that the giants wanted to eat him because they were told that if they ate his flesh, the would gain his ability to shape-shift. They hadn't attacked the house in the past few days simply so they could use Frank's grandmother as bait. While Mars was unsure if eating him would give the giants his family gift, Mars explained that he didn't fight his kids' battles.
The next morning, the Laistrygonians attacked the house, screaming for Frank to give himself up and allow them to eat him. Frank used the weapons in the attic to fight off the giants, but it became clear they would soon overrun the house. Frank, Percy, and Hazel were forced to abandon the house, with Percy causing the water pressure in the water system to explode, allowing them to drive away as they watched the house burn to the ground. The Laistrygonians followed them to an airport, but are unable to catch the group thanks to Frank shooting them with his arrows.
- In The Son of Neptune when Percy, Frank, and Hazel see a group of Laistrygonians outside Frank's house, Percy tells them they are Canadians. This is a reference to what Annabeth called them in The Sea of Monsters as the Laistrygonians live in the north. Frank got slightly offended by that since he is Chinese-Canadian.
- Mars and Frank use the word "Ogre" several times to describe the giants instead of their actual name.
- In The Titan's Curse, author Rick Riordan spells Laistrygonians, "Laestrygonians." This is simply an alternative spelling.
- In the series, Laistrygonian giants have been referred to as Cannibals, Northern giants, Sasquatch, and Ogres.
- While Laistrygonians are called Cannibals by others, this would imply they eat other Laistrygonian giants. However, they seem to only be interested in eating Demigods or humans.