White Harbor is a large harbor town south of Winterfell where the White Knife river opens into the sea. The castle and town has more contact with the southern part of the realm than any other place in the North, and so the Manderlys follow the seven-sided Faith and employ more knights than other houses of the region. White Harbor itself was built by King Jon Stark after driving off seaborne raiders from the east.
Lord Manderly is extremely fat, moreso than even his sons. His he has two sons: his heir, Ser Wylis, and Ser Wendel.
Lord Manderly was intent on marrying Lady Hornwood but when the Bastard of Bolton forced her to marry him and left her to starve to death, Lord Manderly sent forces into the Hornwood lands, occupying them in the name of protecting the Hornwood interests even after Ramsay Snow was apparently killed. When Ser Rodrik Cassel called the levies to deal with Theon Turncloak at Winterfell, Lord Manderly sent barges packed with knights and siege equipment, but he himself remained at White Harbor.
Lord Manderly’s heir, Ser Wylis, was a captive of the Lannisters until freed in the taking of Harrenhal by the forces under Bolton. He was left to hold a rearguard and was once again captured, this time by forces under the command of Ser Gregor Clegane. Ser Wendel accompanied the northman host to the Twins and was killed in the Red Wedding.
Ser Wylis is returned to White Harbor after Lord Manderly agrees to marriages between the Freys and his grand-daughters, and executes Ser Davos Seaworth. However, the execution is of some common criminal, and Ser Davos is hidden away until Lord Manderly recovers his son. He then reveals to Ser Davos that he means to fight for Stannis, provided that Davos can go to Skagos and bring back Rickon Stark, who Stannis must make Lord of Winterfell. Traveling to Winterfell, Lord Manderly pretends to be Lord Bolton’s man… but the three Freys who were present at White Harbor disappear on the way to the castle, and Lord Manderly is suspected. At the wedding feast for Ramsay Bolton and the counterfeit Arya Stark, Lord Manderly presents a great pork pie, and eats double portions with great gusto.
Tensions boil over during the snowstorm, and the Freys attack the Manderlys. Lord Manderly himself is seriously wounded with a cut to his neck, and Roose Bolton commands the Manderlys and Freys to immediately depart Winterfell and attack the forces outside the castle whom they believe belong to Stannis Baratheon.