Necromancer

Most of your knowledge of them comes from Catalina who being in the Dark Order longer had more information about them.

The Vampire Clans from what you know live in a fortress run by Lord Rostov. This fortress' location is unknown and hidden by powerful magic. It is there where those few remaining vampires that have kept their faculties stay. (As opposed to the near mindless ones that lurk in holes in the wilderness)

While groups of vampires may have been involved in their own political intrigues and agendas in the past, the term Vampire Clans now is somewhat of a misnomer since Lord Rostov has a firm command over the remaining vampires. It's basically a dictatorship more than a "council" where they all sit around discussing things. The term Clans is probably kept to just hold on to the illusion of former glory of freedom rather than the reality that they're all hiding in a secret fortress ruled by a tyrant.

Despite their reduced power, they still can affect mortal affairs. Currently they are no doubt affecting these affairs to hinder you. The death of their delegate pissed them off pretty severely, not to mention they don't agree with the "high profile" necromancy in the first place. You received a letter by bat from them recently saying that your actions will not go unopposed by the Clans and that your days on this world are numbered.