From BGG, here are the most recent rules changes for the Shapeshifters and Riverwalkers:
Shapeshifters can adopt new homeland types, right? What is the nerf?
These are the official rules updates for Riverwalkers and Shapeshifters:
Riverwalkers have to pay 1 coin when they unlock a new terrain on their wheel (starting terrain is free), 2 coins if it is another player's home terrain.
- priest gained in Phase I (i.e. as income from temple, sanctuary or bonus tile): the coins have to be either existing coins (saved from previous round) or coins gained as income parallel to the priest; no burning/conversion allowed to get the coins (the player would need to do such burning/conversion before he/she passed in the previous Phase II)
- priest gained in Phase II (i.e. from power action aka ACT2, town tile or direct 5pw-to-priest conversion): the coins can also come from conversion of power/workers/priests
- priest gained in Phase III (i.e. from cult bonus): the coins have to be existing coins (saved from Phase II); no burning/conversion allowed (the player would need to do such burning/conversion before passing in Phase II)
The cost of the Shapeshifter Stronghold power is increased to 5 power / 5 power tokens, and using the power (= shift your current hometerrain into another hometerrain) no longer generates any victory points. They also have to pay one VP for every power token they receive using their faction special ability. So when another player takes power during their build action, they pay 1 VP and get a new power token into bowl III. If the Shapeshifters don't want to pay 1VP, they get nothing (no power gain, which is different from when other players refuse to take power - then Shapeshifters themselves would get one power).