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.
The second layer, Thuldanin, has a petrifying effect on objects and creatures that stay too long. That may be what you are thinking of.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 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.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?