It did go well, the players immediately noped away as the automata animated.
They did their best to please the Ghost of Maria-Valencia ex Flambeau, giving a named oath that they would bury them in grounds of Oakdell, and not to use Christian rights but those of Apollo (or as they'll find out, Apollyon). The party seems happy to have gained a Ghost teacher, and are oblivious to the fact that it's be an infernal ghost... She asked them to wipe their feet when they left her lab (which smudged the ward keeping her trapped there), and upon noticing the ichor, they soaked it up with a rag, and just tossed it back into the room.
They didn't breach the final room to fight Eginolf, but instead, plan on coming back on Halloween (6 weeks later in game) for the fight. Their interpretation is that since there was no loud big bad when they visited, the big bad must only be active on Halloween (and other dates when the Infernal is strong).
Of deceit: the party has a grog with detect (un)holiness and infernal lore, but rolled poorly and did not beat the target numbers to realise that the "magic" was in fact infernal, and rolled abysmally on his infernal lore rolls... What should alert the players that something is off is that when they come back the magic aura will be stronger on a night where the Infernal is normally strong...
As for fitting into the campaign: the mages plan on getting the OK from the local lord, but want to essentially plunder the ruins. Labs and all. They stole a few things: all the books/scrolls, eginolf's sword and armour, as well as the bone dagger (because it was marked with PeCo runes). They checked all the buckets that contained anything for magic (in case it's a bucket of creating basalt/sulphur...). Of all the weird things they chose to nab, the obsidian candles didn't make them worried, instead, there was an aha moment of "oh yeah we could have just used MuTe to make the raw obsidian into wax" when they used ReTe to craft them for the NPC, but no question of "wait, the other guy wants a mute servant and obsidian candles, and we find obsidian candles in this infernal tainted place..."
How it fits with the saga: the Baron dies in this game year and the family has to fight the archbishop to keep the castle, so obviously a spirit of disease got out and did it, the castle stores are going to suffer from demon rats too from now on. And the PCs will have an infernal ghost haunting them.
So far the story as they see it is that Rudiaria messed with a demon lord to try and end a famine, but not that this was part of a long term mistake of being Infernalists...