Source: Eberron Campaign Setting
You have a least dragonmark.
Prerequisite: Member of appropriate dragonmarked race and house.
Benefit: You gain a least dragonmark and the use of one spell-like ability associated with the least dragonmark of your house. A saving throw against your dragonmark spell-like ability has a DC of 10 + the level of the spell + your Cha modifier. Your caster level for your least dragonmark spell-like ability is 1 + your level in the dragonmark heir prestige class (if any).