I think it is a valid conclusion, contrary to what other people think that it was at Ranni's command that the black knives killed Ranni's companions. I think it is very clear that this attack was a revolt by the black knives against Ranni, one of the black knives is even stuck in an evergaol probably by Ranni

It's worth noting that Alecto was trapped in an evorgaol at the top of the moonlight altar, so it's entirely possible that they didn't part on good terms

The black knife assassins (Numen) and the Nox (descendants of the Numen) do not have the same goals. They have the same origins, but the Nox and the Numen so have different motivations. Many of the Numen in a Leyndell, including Marika, converted to erdtree worship and abandoned intellectual pursuits such as sorcery and alchemy/science that those Numen who would eventually become the Nox continued to invest in more and more enthusiastically until such a time as two factions arose in opposition to each other within Leyndell Eternal City. But then the greater will cast down the portion of the city wherein the Nox faction of Numen were most concentrated. In turn creating the nameless eternal city just below Leyndell. At least, that’s my understanding of the lore, which could easily be wrong so take it with a heaping spoonful of whatever flavour enhancement you fancy 🤭✨

this is pure speculation imho. i recently re-read the blasphemous claw desciption, and it suggestz rykard was involved in the night of the black knives, helping ranni : _"On the night of the dire plot, Ranni rewarded Praetor Rykard with these traces. Should the coming trespass one day transpire, they would serve as a last-resort foil, allowing Rykard to challenge Maliketh the Black Blade, the black beast of Destined Death."_

Objection!!!! I have 2 problems with your theory: 1. The attack on Blaidd appears to be triggered by the slaying of the Baleful Shadow, not by Ranni accepting the Tarnished as Her consort, and news of Blaidd's fate to Iji triggers the attack on him. 2. Alecto's imprisonment in the Evergoal on the Moonlight Altar and the item description of Tiche's ashes strongly implies that Ranni and the Black Knife Assassins had a nasty falling out in the immediate aftermath of the Night of Black Knives. Consequentially it would appear that the attacks on Blaidd and Iji were likely attacks made to stop Ranni from ascending to God hood now that her fate was no longer suspended and she had a clear path to eliminate her 2 fingers by eliminating her remaining vassals and her only apparent support to get into the Erdtree and the Elden Ring within. As why the Black Knife Assassins had a falling out with Ranni I suspect they were acting on the behalf of a certain other Emperian reputed to both fearsome and alluring I mean I don't think its a co-incidence the location where the largest number of living Black Knife Assassins reside and where you find the Black Knife Assassin Armor set is in Ordinia AKA the the sealed gate to the Halig Tree.

Gonna be about what? Don't leave me hanging lol xD I definitely think Ranni and the Black Knives had some kind of falling out with each other