extinguish all hope isn't that good due to the fact that it's six mana. it's better off in the sideboard. running Hero's Downfall instead would be a better idea, because then, you also have a way to deal with planeswalkers and you'll probably need to kill creatures earlier on to establish board dominance.

also Whip of Erebos probably mainboard, or at least sideboard it. good for gaining life, and it can set off the constellation trigger with creatures from your graveyard. I understand that you have odunus river traveler, but only two, so a whip could be helpful

Having no way to reliably trigger constellation constantly is the problem of BW constellation. The only way is heliod, but that cost a whooping 4 mana. Even so, the constellation triggers are mech. Grim guardian does not win games, coinsmith is nice in theory, but ultimately fails to deliver until the very late game. having a total of 3 removal spells (E all hope does not count) is very, very bad, as you want to survive to the mid-late game.

Ultimately, the BW constellation deck relies on godlike draws in order to be successful, as most cards are situational and reaching the topdecking stage of the game with this deck sucks.

I would really suggest removing white and going green, if only for Eidolon of Blossoms and Mana Bloom , but the color has a lot more to offer.

The only good white enchantment card is really Banishing Light as it is unconditional removal. White has little to nothing to offer for devotion.

Please note that all comments are made as evaluation vs the current metagame. Everything may change in a month's time.

Thanks for the comments. wasterbaster, those are both excellent suggestions, put them in. Boza, I must admit I didn't think to use green, but you have a good point; I'll definitely look into it after Khans. However, I do think white is still an ok option due to God-Favored General and Dictate of Heliod . Would it be worth going 3 colours?

On further thoughts, taken out Hero's Downfall simply because it's a fair bit pricey, so I'm not actually going to buy them if and when I build the deck. Swapped out Heliod for Athreos as a better way to keep enchantments coming.

Check out my Enchanting Doom deck for ideas.

you should try using Stab Wound in this deck. It would be really fun to use considering the fact you have Grim Guardian to slowly leak life every turn.