I'm trying my hand at midrange Earth/Air here with some undead/cemetery synergies. Probably not top tier but very solid and fun to play. Here's the rundown.

Minions

Barrow Wight was an easy include because it's basically an upgrade to any skeleton you have on the board, especially since it can burrow and still remain a nuisance mid-late game.

Novice Necromancer is there to be a curve filler and cheap spellcaster with a little added value of an extra skeleton.

Sisters of Avalon cut down on variance and provide spellcasting. They also curve into Carrionette for a potential turn 3 beater like Nightmare.

Zombie Bruiser was the best I could do to fill out the 4 mana slots along with Death Knight which is an obvious inclusion.

Daperyll Vampire and Renatus Trueblood were also obvious choices next on the curve and are incredible with magics like Necropotence and Whirling Blades.

Master Necromancer is best paired with Death Knight on curve and makes a decent choice for a mid-game Dream Quest if adequately protected.

Nimbus Jinn is notably not an undead and therefore can't be cheated into play with Carrionette, but is definitely my personal favorite beater in the whole game, and worthy of the 6 mana slot given the other choices.

Draconian Bonekite and Nightmare are deadly wincons but are unlikely to see much action outside of being reanimated, hence why I opted for some card selections spells.

Magic and Auras

Bone Spear gives you some cheap direct damage which can be surprisingly versatile given that you have so many expendable minions.

Browse is a real bargain and cuts down on variance which I generally hate in card games. Use it to put together a good Carrionette combo or just fetch some removal if needed.

Dream Quest can be tricky to use but there are plenty of spellcasters in the deck to make use of it.

Necropotence is a solid buff for anything undead but is especially devastating on one of your vampires. Desecrate is a vastly underestimated offensive spell with incredible value for 2 mana if used effectively.

Carrionette also punches far above its weight for the cost, being able to revive any undead. Hold onto it if your Death Knight gets killed off or use it on something bigger if you managed to discard it with Sisters of Avalon.

Witching Hour was another obvious inclusion and is ideally used after dropping a Master Necromancer.

Black Mass gives you even more card selection and more chances to find a powerful minion to close out the game or stabilize the board as the situation demands.

Cave-In is solid, potentially 2-for-1 removal against minions and artifacts.

Earthquake is great for stabilizing the board or breaking a mid-game stalemate.

Whirling Blades is good on almost anything stronger than a skeleton but especially devastating on a vampire.

Summoning Sphere and Eclipse were both obvious inclusions for any aggro/midrange Air deck and are both worthy selections for Dream Quest or Browse.

Artifacts

Ring of Morrigan was an easy choice for a deck with so many spellcasters and magics. Pnakotic Manuscript pairs well with skeletons if you have extras that aren't serving much of a purpose, or if you have a vampire doing work and can afford the damage to yourself. Toolbox goes in basically every deck I play these days for access to situational utilities relegated to the collection.

Sites

All pretty obvious inclusions given the theme of this deck, so I doubt I need to dedicate a full section to them. I will say that the best ones to mulligan for are probably Wuthering Heights as a stationary Avatar of Air and perhaps Rift Valley for its potential to open up another avenue of attack on your opponent's side of the board. Dread Thicket is also quite good if you can manage to place it forward while keeping enemy minions off of it. Dark Alley is another great forward site but also works as free stealth for a spellcaster which makes Dream Quest a much safer play.