Quote Originally Posted by Lord_Gareth View Post
To what extent to chronomancers influence planar politics? What sorts of foes do they face on a regular basis?
They don't. Chronomancers messing with Big Things get told off in a Big Hurry.

Chronomancers most often have to deal with one another, with the dangers of the time periods they enter, and with the denizens of Temporal Prime, such as temporal hounds, time dimensionals and a few other unpleasant predators. There are also strands, more of an occupational hazard than a foe, which aggregate on a chronomancer as he or she travels and attempt to yank him or her "downstream." They can be extremely annoying.

Quote Originally Posted by Coidzor View Post
Do any of the outer planes specifically erode free will by causing visitors to conform to the ethos of the plane over a period of time by the nature of the plane itself directly (aside from Elysium/The Grey Waste straight-up "eating" even non-petitioners)? As opposed to indirectly, like visiting Ysgard at the wrong time of day and having to do something about the drunk yahoos trying to decapitate you.
Not particularly. Mechanus will annoy you, Limbo will confuse you, but in general being on an Outer Plane would have no impact on you different from, say, living in a Material Plane community of a certain character over a span of time.

When Acheron gets brought up, it seems like visitors end up getting twisted into going native if they don't leave quickly, and I couldn't tell if that was canon or fanon or a misinterpretation on my part.
The second layer, Thuldanin, has a petrifying effect on objects and creatures that stay too long. That may be what you are thinking of.

What are the majority of armies on the Cubes in Acheron comprised of anyway? I recall that portions of the Blood War are fought there, but my impression is that those aren't even close to a drop in the bucket, nor are the various factions that exist there purely because of various Powers giving afterlives of Total War to their petitioner followers. Is it a hodgepodge of the detritus of the planes and prime worlds, with various factions made up of petitioners, planar refugees, traders who stayed an hour too long negotiating a contract? Is it that petitioners make up the majority of the armies rather than becoming any kind of proper outsider or fiend?
The Blood War doesn't touch Acheron; it's not in the way. What does go there are major conflicts between powers, as well as the armies of the kobold, goblin and orc deities, who wage great and terrible wars on one another. Their armies are comprised of some few living members, a large number of petitioners reshaped into soldiers, and the odd fiend pressed or paid into service.