by Galandil
This problem is similar to the one in the FAQs about Into the Heat + Shocktroops.The thing with the Immediate Effect rule is that we can execute all the contradicting effects in two possible ways:
1) FIFO - the last effect played overrides the previous effects in the same turn
2) All the effects are applied, and in case of contradicting effects, the player applies only the worst ones - in this particular case if we have Mountain spaces cost of 5 AND Mountain spaces impassable -> Mountain spaces impassable, regardless of order of card play.
I think that knowing which one Vlaada considers valid between 1 and 2 would answer definitively this conundrum + the ItH/Shocktroops one (and possibly others).