Your misplaced anger seems to be only rivalled by your ignorance.
Have you actually read any FFG books? The Deamon Hunter book?
Because they continually refer to the Grey Knights CHAPTER.....
Or how about Forge World's own Imperial Armour books?
Siege of Vraks, Part III, page 8: - the secret Grey Knights, an entire CHAPTER of the Adeptus Astartes dedicated to the combating and banishment of Daemons.
When they hear that Klightus and Brutus are 'following' Duquesne into the vault the other three are not overly concerned and Solomon spent a bit of time wondering wtf just happened with the servant. Then over their com-beads they heard Brutus exclaim that Duquesne had just ambushed him and stabbed him with a dagger. He was now paralysed. Klightus reported that he could see she had inscribed something on the floor. Klightus normally goes out of his way to avoid contact with any actual heretical practices/writings/artefacts etc. He is jsut a hive scum that helps get the experts where they need to go and helps to handle politics etc. So it was another clue that he immediately went "&%$£ it I'm going in."
The others hustle to their friends' aid. I told the other GM that regardless how quickly they move the situation is the same when they arrive, as it is a setup to get Solomon to use the ritual and therefore give away how it is done. So when they burst in they could see Klightus in the centre of ritual circle with blood running from his eyes, mouth ears and nose. They could see Brutus with a clearly slaaneshi dagger (that they have seen in relation to Duquesne before) stuck in his shoulder, with some sort of dark shadow creeping up on him. Duquesne was stood behind Klightus clearly (to those with the right knowledge performing a ritual to summon a slaaneshi demon into Klightus. I delibrately went "Can I describe it please?" to the other GM and then said what was happening to Klightus with him adding a "nice extra details!" as a slight clue.
The three of them of course began trying to disrupt the ritual: Cortez charged towards it but was held back as though running through treacle. Flare moved to help Brutus and started fighting the shadow. Solomon tried to shoot Duquesne - but the bullet veered wide, then he tried to use his sorcery to get next to her - but was blocked just like other psykic powers. This was delibrate GM flange to come up with some way to stop whatever they tried from working. I hasten to add this is not good practice normally IMO but in this case I really wanted him to have no choice - after all that was the whole point of the dream. After a few rounds of this cortez gave up and went to help Brutus. He pulled the dagger out freeing Brutus but was then posessed by the demon on the dagger. This was another clue that it wasn't real as Cortez's identity is almost wholely based around the fact that he is the guy to deal with that sort of thing. He started fighting Flare whilst Brutus forced his way into the circle (continuing to make it look like he is being the focus of the story) draws various weapons that continually start to float away from him. It was at this point that Solomon's character starting saying things like, "This makes no sense, I can't do any powers and yet her sorcery works," and "There is nothing we can do!" I, still sitting in a player seat, started passing him notes about how he did know a way to stop this. He pointed out that if his sorcery didn't work then a ritual shouldn't either but I assured him that if her ritual was working then it was logical that his could too. This was the point at which he finally twigged and I swapped to sitting behind the GM screen, to much hilarity from the players in general.
Whilst the others continued to mess around failing to stop things coming to a head and the other GM's character Devi ran in persued by the now alerted staff Solomon stayed untouched wondering what to do. He actually considered doing the ritual to save Klightus. He made a willpower check to realise that he could will the components for the ritual into being and that was when he knew for sure that it was not real. He then paused a while to try and determine if any of the others were actually their characters but decided that regardless he had to get out without revealing anything, and promptly shot himsel in the head with a cry of "Death FIrst!"