I noticed a discernible lack of Chaos Wastes threads in this forum, so let’s change this
I am not sure where I read the comment anymore. But I remember someone saying that the influence of the Chaos God watching over an expedition is pretty minor. Effectively, this means only that the final arena map will be cursed by said god (and for the Citadel of Eternity also the fourth map). Other than that there is no influence of them to be noticed. Not even a higher chance for getting curses of the watching Chaos God.
From a gameplay standpoint I understand this because you don’t want all maps in a campaign be cursed by the same Chaos God. It will become boring to tedious. On the other hand it feels wrong to have a Nurgle Expedition and get three times Slaanesh for subsequent maps.
As such I would like to propose an additional (and unlikely to be implemented) element connecting an expedition to a Chaos God: Champion(s) of Chaos or Warbands.
While the U5 are not the big players in the Endtimes, they have been annoying enough that killing them should grant Chaos worshippers some favour from their gods. As such in the terror event of the second map (or maybe randomly first/second/third map) you will get to fight a Champion of Chaos associated to a specific Chaos God (or a Warband if that is easier to design). They shouldn’t be necessarily be on Lord Level but should be stronger than Chaos Warriors or Skarrik.
I don’t want to go to much into design for all of this because I don’t have enough ideas on it. But everyone one is welcome to make suggestions. Basically these Champion of Chaos can be from the Northern Tribes. Considering the high density of Beastmen living in the Chaos Wastes there is also the obvious solution of Beastmen Champions, namely: Khorngor, Pestigor, Slaangor and Tzaangor. From a quick search not much lore about them could be found (they are mentioned in the Army Book for Beast of Chaos sixth edition). This means there should be a lot of creative freedom. Generally, they are tougher and wear more armor than usual beastmen. For two I had random ideas (not sure how feasible):
Khorngor: As mentioned tougher and better armored than normal Bestigors (like much tougher). Works basically as a moving banner as long as he lives. This means that each enemy AND the players get an increase of 2 % attack speed every 10 seconds the Khorngor is close-by up to 50 %. Also, he can and will block all ranged attacks unless he is actively swinging his weapons at one of the players.
Tzaangor: As mentioned tougher and better armored than normal Bestigors (like much tougher). Works on deception. In praxis this means EACH time someone is pressing “F” (or whatever button they keybound the career skill), the Tzaangor will swap places with a random player (obviously this will only start working after he enters the arena). By this swapping mechanism he can swap players into hordes and can avoid all damage career skills. So not using the career skills would be the easiest way for defeating him as you then keep control. But maybe the remaining enemies force your hand. I think it is kinda entertaining to imagine a BH using the career skill just for the Tzaanfor to swap place and another players getting headshotted.
I have no particular ideas for Slaangors (really difficult) or Pestigors (some kind of debuff maybe). If Champion of Chaos are not suitable it could also be Warbands of 5 to 10 tougher Bestigors with a Chaos God specific banner (there was a thread somewhere suggesting lots of banners).
EDIT: Also forget to mention. Upon defeating the Champion of Chaos (and completing the map) you will be already granted the first of the two chests you get right now for completing an expedition. As such there is a better reward if you fail in the latter half of the expedition. Technically, this is not an issue as the game communicates to the server between each expedition map anyway (as seen by the progress in Weekly Quests even for failing expeditions).