As the card base expands, Mountains and Forest continue to be under-used, while cards with special abilities continue to be used more and more.
I would like to suggest a very simple switch that will help balance the game.
Make Kreid-Moor grant immunity to ALL of the creatures in a players’ squads instead of just Mountains creatures. It could also help to make the card faster (4 is very slow for a terrain).
Immunity is becoming more and more important in the metagame, but Kreid-Moor is never used because triple-Mountains is very weak and nobody plays it. This card can suddenly be a useful — and not overpowered — card for Mountains, usable in Plains-Mountains-Dark or Plains-Swamp-Mountains combos, for example.
For your consideration.