Merren Vethar is a Veden highprince. He murdered Theren’s father during the Veden civil war, took his shardblade, and took his highprincedom.
The party has interacted with Merren once, where he tried to arrest the party at the Vedenar docks. He was scared off by Nucko who used an illusion to imitate Theren’s father which caused Merren to run away.
Merren has claimed that Theren and his father were “oppressive” to him and his family, and ironically Theren doesn’t seem to remember him.
Merren has asked King Taravangian for an alliance with his house in an attempt to solidify his power.