Umbric

The sideboard makes no sense

Dark ritual...?
Shepard?
Carrion?
Grim Grin?

At Puschkin, I never said "strictly better" I simply said better since it's more often than not going to used as a removal for planeswalkers, large fatties, enchantments etc.

Missing Martyr of sands

I would also argue that card draw like gitaxian probe, think twice, Peek, or sleight of hand are generally better than Divination, considering all are one mana and some are instant speeds.

Isn't echoing truth just better than Disperse?

Force of will is a must have in legacy

Prone to so much removal, I don't think this could ever be viable actually

I ran a deck very similar

http://www.mtgvault.com/umbric/decks/art-of-artifice/

Drown in sorrow strictly better than Infest

Would also add grave titan, Unholy Grotto, and possibly lord of the undead

Do you even magic? I'd rather have a sorin ult being useless than snapcaster mage lightning bolt, gifts ungiven decks, or any graveyard based decks out there. You have to look at the bigger picture, sorin makes emblems which are amazing and tokens that gain you more life, the ultimate isn't what makes a planeswalker good

Exactly and your opponents fliers stronger, a 5/3 vedilion clique is nothing to scoff at

http://www.mtgvault.com/umbric/decks/spirit/

Personally this is what I would run

Better take a look at Gavitational shift, ALL flying creatures get +2/+0 and ALL creatures get -2/-0. Favorable winds is a better mainboard piece than Gravitaional shift, reason being, this is a aggro deck with an already high mana curve, only your creatures with flying get buffed. With GS, Twilight drover and Geist honored monk become worse as does tokens made by sorin and so does doomed traveler.

Why is favorable winds in your sb?

I favor no gods I "DECIDE" my own fate

(Born of the gods)

Nyxthos shrine to nyx

Must've been difficult to make

Honor of the Pure, zealous conscripts, raise the alarm, Martyr of sands, are great and cheap!

As for the sideboard:

I would definitely mainboard Honor of the pure, there's just no point not to. Hero's downfall is solid but not all that great for sideboard, if you're looking for good spot removal might as well use doom blade or a slightly more expensive Path to Exile and I would mainboard that or tragic slip.

I wouldn't keep shared triumph in the sideboard because this deck is so close to being modern legal and good! Mausoleum guard isn't great sideboard material and not all that great.

I would add sundering growth for atrifact decks and Rootborn defenses against Control decks who use board wipes.

Garveyards are used a lot in Modern so Relic of Progenitus, Tomod's crypt, rest in peace, grafdiggers cage are all cheap, good and legal in modern.

For Affinity decks (decks that use a lot of cheap artifact monsters) I would add Stoney silence

You could also mainboard beckon apparition

At least inkmoth

Might as well add invisible stalker and phyresis