- "Never burn a bridge unless your foe is on it, Captain."
Lord Selnikov first appears as a resident of Balan's Gap and co-conspirator of Princess Anevka Sturmvoraus. He is a member of the Knights of Jove, re-purposed to supporting the return and success of their Mistress, aka the Other, aka Lucrezia Mongfish. He is somewhat overweight and, as hinted by the page image, may have something of a drinking problem. He shaves himself because he doesn't trust anyone he knows to hold a razor to his throat.
Following the death of Aaronev, Anevka appears abruptly at Selnikov's residence and orders him to ensure the deaths of all the theater attendees who imprinted upon Agatha's voice when she was performing on stage in the palace theatre. He also assists in the imprinting of the rest of the townsfolk to Anevka's modified voice, and her staged assault on Sturmhalten Castle. Previously, he worked to scrub any traces of the Knights' involvement in the modified Revenant outbreak in Passholdt, and recovered the miniature prototype Hive Engine that is eventually used on Klaus Wulfenbach.
Lord Selnikov later reappears using the title "General Rudolf Selnikov, Commander of the Knights of Jove." (At first it had been plausible that Lord Selnikov and General Selnikov were two separate people, but it has since been established that they are one and the same.) His Lordship leads the war-stomper invasion of Mechanicsburg on behalf of House Valois. This is part of the Knights' attempt to restore the Storm King's line to the rulership of Europa using manipulation of legend, circumstance and timing to their best advantage. Unfortunately for the General, he is summarily by a very determined Gilgamesh Wulfenbach in a massive, artificially-generated lightning strike.
Though officially dead, Selnikov's head is retrieved by Captain Vole under instructions by Gil to deliver to Dr. Sun for revival and memory retrieval. Revived inside a glass jar, he/his head is given a leonine offer of alliance with the Wulfenbach Empire to protect him from any reprisals from the Knights of Jove, against whom Selnikov compares the Wulfenbach administration favorably in terms of safety against deadly intrigue.
He is later consulted by Boris Dolokhov over the use of modified slaver wasps on Sparks and the effect of the Madness Place in this process; it is never explicitly stated, but it appears that Boris suspects the truth about what happened to Klaus.
Married, but unhappily. Apparently he is regularly unfaithful; the print novel Agatha H. and the Clockwork Princess mentions his wife is shopping in Paris while Rudolf has a implicit affair; his focus on this means that he doesn't hear about Aaronev's death until Anevka appears at his house. Since he was revived after death, he is considered officially dead in the eyes of the Fifty Families, and his revert to his "insufferable nephew." On the upside, he is also officially no longer married.
It should be noted, however, when considering his lack of marital fidelity, that according to Agatha H. and the Siege of Mechanicsburg, it is not necessarily the case that Lady Selnikov fails to excite him, but rather the opposite, as their closed door activity upon her return from adventures evidently leaves him both "physically fit" and with a "perpetually hunted look".
Said Lady, his widow, is later revealed to be Margarella Selnikov, fleeing from assassins in the employ of the Knights of Jove and enacting her own agenda against Martellus von Blitzengaard in concert with The Immortal Library.
Incidentally, the above-mentioned nephew is quite likely to be Tarvek, but at Martellus von Blitzengaard has not yet been . Martellus is far more insufferable than Tarvek, who has successfully cultivated the image of a feeble-minded fop.
Lord Selnikov also appears on one of the cards in The Works as a living "head in a jar". And now, thanks to Doctor Sun, he looks just like himself. Lord Selnikov's card details are Villain and Spark. While the former is fairly obvious, no evidence of the Spark has been displayed as yet in the canon (unless the War Stompers he led were his creations, but again, this has not been said or shown).
The Works also contains a card for Lady Selnikov.