[Arryn]

Originally posted by archaeolept:
no. immortals are not supposed to retreat when in friendly dominion; but it does seem likely that the occupation of her capital vitiated this somehow.

I've seen immortals retreat in friendly dom. If this is a bug, it's been around a while. Given that Merry's capital was occupied, as well as surrounding lands, there's a good chance that there wasn't positive dominion in the capital at the time of the rout check.