You're correct about the quick replacements that normally follow a Kell's death, such as between Rezyl Azzir killing one of the Devil's Kells and the rise of Solkis to leadership, but remember that since the latter's death, Riksis had been calling the shots until his untimely end. It's quite likely that he had taken measures to eliminate any potential claimant before we killed him, leaving the house decapitated afterwards. Case in point is that the only lesser nobility (i.e. Barons/Baronesses) we encounter in-game is a Baron of another house working with the devils.

No one said Yor was an iron lord. He was man that let doubt into his heart. He was corrupted by darkness, siva is a whole thing of its own.

That's very interesting. It could very well be the original Kaliks Prime, since it had gone into hiding after the reef wars and the Servitor encountered in the Prison of Elders is just a replica.

Sepiks is coming back which means it still is their servitor so it's unlikely they would have a different servitor as well who is our big boss for the raid. A war mind is also a machine though and would explain the images we have seen that look like Rasputin's bunker (I don't think it's Rasputin but it would make sense that other war mind bunkers looked similar).

well here's the thing if you need extra ether than the prime servitor is already dead. Not to mention that it doesn't matter whether they could or not. In the end Efrideet is a powerful machine and the fallen would choose a machine God over their current kell. In any case Efrideet could easily eradicate the house of devils leadership. But that's exactly what I mean, it's something you wouldn't see coming. It's perfect