The Four Great Houses (四大名門 Yon Daimyōmon) are the Erebonian Empire's four greatest aristocrat families in the Trails Universe. Each upholds the highest of noble traditions and influence over the Imperial provinces by the entrustment of the emperor.
- NOTE: The bold names highlight the primary default lords in each household.
- Duke Cayenne: Current lord of the Lamarre Province and leader of the Four Great Nobles. He was also revealed to be a bloodline descendant of the royal Arnor blood following the removed Royal family member, Orthros Reise Arnor. Like ancestor, he was subsequently removed from power after the civil war's end.
- Helmut Albarea: Lord of the Kreuzen Province who holds the title of "Duke". Forced to step down from power after being arrested by his second son for his renegade transgressions.
- Rufus Albarea: First-born son of the duke who is one of Thors Military Academy's board of directors. He was secretly an Ironblood member to take the Noble Alliance down from the inside as their head tactician.
- Jusis Albarea: One of the Class VII protagonists who is the duke's illegitimate son. After the events of Cold Steel 2, he took up the role of Kreuzen's new lord after his father's removal.
- Gerhart Rogner: Lord of the Nortia Province who holds the title of "Marquis".
- Heidel Rogner: The marquis's younger brother who became Reinford Group's new director following the Noble Alliance's hostile takeover.
- Angelica Rogner: The marquis's delinquent daughter who supports Rean and her Thors classmates companions against her father.
- Fernand Hyarms: Lord of the Sutherland Province who holds the title of "Marquis".
- Patrick T. Hyarms: The third-born son of Marquis Hyarms who attends Thors as Rean's rival.