My opinion on the new cards

[Maximvs]

Any card not mentioned is totally fine.

Arctic Shelter : I highly question the introduction of a generic shrine, playable by any deck, that is more powerful than the green, color specific shrine. I consider the igloo superior because you do not need to repay the mana cost of the creature when it reenters play, an advantage that seems more of a pro than the con of being frozen.

I suggest that the player loses mana at the start of his turn equal to the cost of the creature coming out of the igloo, so the frozen becomes the con to the pro that is a shrine possibly played by all decks.

Devourer of worlds : This is a card that seems to go against the concept of Spellweaver ; that we can accurately guess what your opponent can do. This card can screw up a lot of decks and it can be played by any deck, comparatively to, let's say, a cataclysm you know the opponent can only play with 2 dominion and 6 mana. I suggest a slight nerf, perhaps making it a 1 speed.

Helm of righteousness : Interesting card, but it has 3 things I don't like much ; you can make a complete deck of it, which gives an absurd result, it's yet again another card that destroys mid range decks rather than rush decks and it sure is powerful in decks like one turn heal. What I suggest is that you introduce 'secondary' cards, cards that can be put in a deck a maximum of 8 or 12 times or such, to limit the absurdity of it.