Never Die

Yeah, the only weakness this deck has are field wipes. Things like Day of Judgement. You might consider changing 4-6 of the plains to multicolor lands (white/blue) and side boarding counter spells, so when a field wipe shows up you have a way to stop it. If you want to do that I recommend Glacial fortress and seachrome coast, my build of lands would be 4 fortresses and 2 coasts and the rest be basic plains. Cards I would sideboard would be things like essance scatter, negate, counter, counterbore, etc... It'll increase the cost though, don't know how much but cost will go up.

Upon discussion with my friend who is a better deck builder than I am, we both agreed that splashing green would also be a good choice if not better then blue. Sideboard asceticism if you do this. (green is probably the better choice because you get more space in your sideboard)

It would work, its just a way to make sure your opponents can't kill cho-manno or destroy the enchantment. And the shroud mechanic no longer exists. Whenever you see shroud, replace the word with hexproof. Does the same thing only hexproof lets you cast stuff on your creatures. And I'm sure there are better decks than this one, I'm far from a great deck builder. This is what I came up with in 10-15 minutes. Obviously you sit on the cho-manno, and then ding away for a little damage at a time with your spirit mantle enchanted creatures till the game is over. Remove troublesome things like planeswalkers with the oblivion rings.

Let me know how it works out for you if you try it. I might do the same now that I think about it.

shroud does still exist. oth mechanisms exist. Just no cards will be printed any time soon with shroud. googled it cause u just gave me hopes :D