The House of High Lords is the upper body of the bicameral legislature of Valyria called Parliament. The Great Charter of Valyria describes seats in the House of High Lords as being welcome to every Magnate of Valyria, which is to say, every duke and count throughout the whole kingdom.
The House of High Lords is presided over by the Lord Chancellor, who is the second of the Great Officers of State, and the possessor of the Great Seal of Valyria, which means that Parliamentary acts which succeed on a floor vote can pass under the seal and gain the power of binding law for the kingdom. Bills which are passed up to the House of High Lords from the lower house, the House Comitates also are debated and voted by the lords before they too are passed under the seal.
Both dukes and counts receive one vote each in the House of High Lords, and counts receive only one vote even if they are grand counts. However, as of the time of this writing, there is discussion of allowing the appointment of viscounts of a number up to the total merged counties in a grand county. Viscount would be a new peerage title recognized by the College of Heralds.