Least Mark of Death: Deathwatch 2/day, Gentle Repose 1/day or Death Knell 1/day; +2 bonus on Intimidate checks.
Lesser Mark of Death: Death Ward 1/day, Inflict Serious Wounds 1/day or Speak with Dead 1/day;
Greater Mark of Death: Harm 1/day or Undeath to Death 1/day
Siberys Mark of Death: Symbol of Death 1/day.
As I see it, House Vol had the Mark of Death, not the Mark of Undeath.