This is gonna take some wall of text to explain. Here we go
In the current campaign our warband came to Landunder (Calixis sector) to investigate the case of people massively disappearing (many millions). Shortly after arrival our divination psyker did some scrying and was detected by a powerful rogue psyker on the hive who is in part responsible for the occurence. We know his location. He belongs to the brotherhood of horned darkness (canon thing) (chaos undivided)
The whole thing apparently operated through a thing called Tontine pact. Common people sign it and if one of the signed dies, others get portion of the deceased one's possessions. Adeptus ministorum outsourced the issuing and handling of the said pacts to some guild and well, the pacts themselves are tainted. Produced this way to indirectly bring people under certain effects. They all get tainted too and apparently there are multiple "mini incursions" happening throughout the whole hive. If those people die, the patron demon of the cult get their souls, if not said incursions happen. In like 3km radius there is an incursion where demon comes, snags the civilian and drags it to the warp and returns there. within couple of minutes munitorum guards come by to pick up all the deceased stuff (couple minutes, aka they know beforehand) thus leading to conclusion that they are involved too which is worrying. How deep does this go?
Our psyker tried more scrying and well, the rogue psyker can summon demons at will apparently and that happened. Got attacked. Aka "dont poke your nose where it doesnt belong".
So at this point we have 1 player infiltrating the guild and confirming that the guildmaster is corrupted (apparently they produce those pacts already corrupted, etc) and he got captured :D Have imperial guard corruption (and we dont know how high it goes) and a powerful rogue psyker. Everyone is "itchy" drawing poisoned knives at the moments notice and no clue how to operate further. We wanted to do things subtly this time around but already got caught scrying which raises suspicions. As such I'm thinking that we could make up a new tzeentchian cult which supposedly started operating here and pin our actions on them. Maybe catch some cultists and stage a fake tzeentchian sacrificial ritual or something. Not sure how to check the depth of corruption within imperial guard or hive as a whole, I guess and hesitant to attack the psyker as it would immediately raise red flags and we dont know enough, nor have enough firepower to deal with them. Seem kinda stuck. If we found out enough, might maybe solve it indirectly. Tipping the adeptus arbites (if uncorrupted) or sending word for assistance as it seems like the cult has spread widely.
Any suggestions on the situations? (hopefully not an exterminatus :DD)