Ramp-less Varina

This deck looks to take advantage of Varina's first ability by playing as many zombies as possible in the first three turns of the game. This plan does not work well with having ramp in the deck.

Zombies

The zombies in the deck (the vast majority of which cost three or less) serve mostly one purpose: triggering Varina. This partly explains the choice of cards that are not exactly commander staples (which is one of the reason I like this build over the first versions I played). There is also a will to have blue zombies (for Force of Will and Force of Negation).
The only 4 and 5 drop zombies either provide evasion (Vile Entomber, by searching wonder or Hordewing Skaab, for obvious reasons), are just very powerful (Gray Merchant of Asphodel to help finish the game, Undead Warchief to get big and wide - if it survives the turn it hits the board, or Repository Skaab for the way it interacts with mass reanimation spells).

Tutors

Apart from the classics (Demonic Tutor, Vampiric Tutor and Diabolic Intent), I play Entomb (generally good in this deck) and Mausoleum Secrets (that will be able to get what's needed depending on context - mass reanimation when the graveyard is full of zombies or mass removal with three or four black cards in the graveyard).

Removal

Nothing surprising here, cheap removal. I play Despark over Anguished Unmaking, because one mana is a large difference in this deck. Supreme verdict is mostly there because it is a blue wrath.

Protection

Free stuff and Miscast (currently in testing)

Good stuff

Phyrexian Altar is an infinite combo with Gravecrawler and a pinger, such as Wayward Servant and can save creatures of exile.
Wonder makes zombies fly, for more Varina triggers.

Card Draw

Cantrips, Teferi's Ageless Insight (the cheapest of these effects, interacts very well with Varina) and Mission Briefing (to recast a reanimation spell in the late game, or a counter or removal earlier).

Overall, the deck is a lot of fun to play with a lot of decisions to make. It is active from turn one and generally plays spells until the end of the game. If you enjoy being the archenemy (as you'll be the first on the board most of the time).

Note: the current version of the deck takes the concept to a more "extreme" level, where everything works towards the same goal. It may be better than previous versions, may be worse, but that is the fun of brewing, isn't it :)