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When his nephew Lord Umber marches south to answer Robb Stark's call to arms, Mors and Hother are left as joint castellans. However at the Red Wedding the Freys and Boltons murder Robb Stark and most of his army, including Hothers' great-nephew Smalljon Umber, heir to Last Hearth, and capture many nobles including the Greatjon.
Hother Umber reluctantly joins Roose Bolton, who has been made Warden of the North by the Lannisters, as his nephew is held captive. When Stannis Baratheon arrives in the North Mors agrees to join Stannis if he is not forced to fight his brother and if they receive a pardon. Hother takes the old men of Last Hearth to Winterfell, while Mors takes the green boys. In Winterfell Barbrey Dustin tells Aenys Freys that if they did not hold the Greatjon Hother would pull out his entrails and make him eat them.
- It is theorised Hother and the old men are planning to attack the Boltons and Freys, dying in the attempt. It is known that in the North during winter old men go off to hunt and never return so there is more food for the younger people. Hother in "A Clash of Kings" mentions that due to the Greatjon taking so many men they have been unable to get much of the harvest in, meaning food could be short at Last Hearth, therefore the old men are going with the intention of dying so there is enough food to last through winter. If so Hother may be dead by "The Winds of Winter".