LIFE ISN'T FAIR...SO TAKE IT BY ANY MEANS NECESSARY AND PAINT IT BLACK
Sometimes the best unions are made with the most diametrically opposed allies, and thanks to Teysa, Orzhov Scion, now you can turn every day into April 15th and celebrate as if you were the IRS. The old adage that speed kills has never been so true, and the reality is you don't need to kill anything directly, you just need to make sacrifices with the right pieces in place to gain infinite life and/or drain infinite life and combo to a win. Just like life and death, black and white are in perfect harmony in this deck, which makes for an awfully successful life-taxing team. While the color balance of the deck slants toward white, just like The Rolling Stones, you'll want to paint it black to win.
There are many options to be used in this deck concept, which can easily be built as more of a stax deck, but this build is more straightforward with its less than ulterior motives using the commander's ability to create infinite creature tokens, resulting in endless sacrificing and life gain and life drain combos. I've done my best to create a fairly quick and complimentary build that will outpace your opponents ability to effectively stop your progress. With Teysa, Orzhov Scion at the helm, gaining life and draining life from creature ETBs or death triggers should be fairly consistent to accomplish. The redundancy of Corpse Knight, Cruel Celebrant, Vito, Thorn of the Dusk Rose, Marauding Blight-Priest and similar effects provide numerous possibilities to reach that goal, especially as all of the combo pieces are CMC 3 or less. Teysa's goals aren't exactly subtle, so keeping her safely in the command zone is often the best plan until the combo pieces are ready. As your two combo-completing staples, once Darkest Hour or Painter's Servant hit the board, comboing off should happen immediately. As a very strong alternate combo backup line, Leonin Relic-Warder and Animate Dead or Dance of the Dead can also do the job.
AUDITING YOUR DECK AND YOUR OPPONENTS TO VICTORY
The most important combo cards in the deck are Darkest Hour, Painter's Servant and Leonin Relic-Warder, as your ability to combo to a win with any of them generally happens at instant speed and are difficult to interact with once they resolve. Depending on your board state, playing the first two without the ability to sacrifice other creatures is a recipe for disaster, so make sure they are the final piece to the puzzle before putting them into play. If either one gets exiled, you still have the other to complete the combo, or the fall back of Leonin Relic-Warder, so the deck is more resilient than a one-trick pony. Using a free sacrifice outlet like Blasting Station, Phyrexian Altar, Ashnod's Altar, Altar of Dementia, Spawning Pit, Carrion Feeder or Viscera Seer gives you the ability to respond to any instants played, so as long as you have more creatures available to sacrifice than your opponents have instants to cast, they won't be able to stop the outcome you've set up.
The other important pieces for the available combos include any of the creature ETB life gain and/or life drain options including Blood Artist, Corpse Knight, Cruel Celebrant, Zulaport Cutthroat or Ayara, First of Locthwain, which are among the best options to drain or nuke your opponents. Altar of the Brood and Altar of Dementia provide for a couple alternate win conditions as they can mill opponents to death if they lack a reshuffling option in their library. The deck is otherwise designed to slow your opponents plans by including card options to answer creature threats (Path to Exile and Swords to Plowshares), prevent combat damage or plays/combos that would otherwise heavily tilt the board state in their favor (Martyr's Cause and Teferi's Protection), as well as limiting opponent tutors and limiting them to playing spells during their turn with Opposition Agent, Aven Mindcensor and Grand Abolisher.
The deck has been designed with low CMC spells and creatures to quickly create a board presence to complete all the parts of the combo lines in a single turn as well as force our opponents to use their early responses/removal to clear the path for our commander plus Darkest Hour or Painter's Servant to complete the combo lines. Even if we're hit with targeted creature removal or a board wipe, reanimation options like Unearth, Reanimate, Sevinne's Reclamation and Recommission become effective ways of recycling our most important creatures and artifacts.
Take a look and feel free to provide suggestions if I'm missing some other options, as I'm always interested in improving the deck's function. As always, thanks for looking and happy brewing.