Dragonmark Houses get their names and their power from Dragonmarks – magical birthmarks resembling tattoos which give their bearer special magical powers. These Dragonmarks run in families, and over many hundreds of years, Dragonmarked Houses have each come to dominate a commercial specialty based on the power of their respective Dragonmarks.
- House Cannith - A human house carrying the Mark of Making, specializing in construction.
- House Deneith - A human house carrying the Mark of Protection, specializing in mercenaries
- House Jorasco - A halfling house carrying the Mark of Healing, specializing in healing
- House Kundarak - A dwarven house carrying the Mark of Warding, specializing in security and banking
- House Phiarlan - An elven house carrying the Mark of Shadows (shared with House Thuranni), specializing in entertainment (and secretly in espionage)
The following are the remaining houses in Eberron, but not yet in DDO:
- House Orien - A human house carrying the Mark of Passage, specializing in postal services and freight shipping
- House Ghallanda - A halfling house carrying the Mark of Hospitality, specializing in bars and inns
- House Lyrandar - A half-elf house carrying the Mark of Storms, specializing in transportation and weather control
- House Medani - A half-elf house carrying the Mark of Detection, specializing in detectives and bodyguards
- House Sivis - A gnome house carrying the Mark of Scribing, specializing in notary services
- House Tharask - A house with both humans and half-orcs carrying the Mark of Finding, specializing in mercenaries, tracking, hunting, finding, and sometimes mining.
- House Thuranni - An elven house carrying the Mark of Shadows (shared with House Phiarlan), specializing in entertainment (and secretly in assassination)
- House Vadalis - A human house carrying the Mark of Handling, specializing in breeding and animal handling.