I'm fairly new to Warhammer 40k, and in a week I'm going to be GMing a GURPS campaign, where the premise is that the party, (made up of three fairly seasoned players, also new to the lore), are going to be playing as a group of Underhive Gangers. For whatever reason, they've decided they want to play as a group of Khornate Cultists, recently corrupted after the splitting of the Imperium, and have the campaign be based around them spreading a Khornate Cult and eventually overthrowing the Hive World in an attempt to gain Daemon Princehood. I liked the idea of GMing a heretical cult better than a street gang, so we'll be rolling with it.
The only problem is that I'm new to the lore, and while I understand the basics and have read through the Lexicanum and 1d4chan, I'm at a loss for ideas. My question to you is, what would a fledgling Khorne Cult run into as they expanded on a standard Hive World, how common would other Chaos Cults be, how quickly would the Inquisition crack down on them, and what kind of mutations would they develop as they shed Blood For The Blood God?
Thank you for answering, I'm sorry if this is off-topic. If they manage to takeover the Hive World, I'm planning on having them fight to the death to see which is worthy of becoming a Daemon Prince, is that in character for Khorne? How do I roleplay a Khornate fanatic, and apart from Sorcery and cowardice, what does Khorne despise?