Fenza has a few tricks up her sleeve being in Abzan that allow us to not only stall but - in some cases - hard lock the board. The Deck can quickly work into a combo state, but it's better to remain passive early game, building upon Stax elements and overall board presence, to push a win mid-to-late game.
Archon of Valor's Reach: perhaps the most underrated Card in this list. When Archon hits the Battlefield 99% of the time you will say "Instant". Why is that? Our combo relies on Animate Auras (Enchants) and either a Creature or Sorcery to finish off our Opponents. None of our game is dependent on Instants. However, various other strategies in cEDH rely heavily on Instants. Let alone the fact that almost all removal found in cEDH is Instant based. One of the (increasingly rarer) pieces of removal is Toxic Deluge, which can shut Archon down, but otherwise we'll be protected from counter magic and removal on our Turn when we're looking to combo out.
Bane of Progress: not too typical in cEDH play, but highly worth it provided the board state gets out of hand. Abzan has no problems powering out a 6cmc "Destroyer of Stuff," especially in a list that utilizes Gaea's Cradle and 28 Creatures. However, most notable about this bomb is the fact that you can Necromancy or otherwise pull him from the Grave to explode everything again! With the variety of value Artifacts & Enchantments, Bane puts us ahead and leaves everyone else behind.
Eidolon of Rhetoric/Ethersworn Canonist/Deafening Silence: we want the games to progress slowly. These Cards accomplish just that. As our main combo relies on both Razaketh, the Foulblooded and Leonin Relic-Warder, we're able to decommission any of these Cards provided we're looking to combo out. Better yet, someone will be forced into using resources to remove these as rarely any combo (outside Flash/Hulk) wins with just one Card. These are great ways to stall the board and work alongside our "Creatures Matter" package.
Elesh Norn, Grand Cenobite: more often than not, this Deck causes the board to devolve into a beatdown plan. As such, we are always the best equipped for this. Anafenza buffing everything as she swings and the sheer number of Creature based utilities allow for Elesh to help us close out games with Damage (crazy, I know!). More of the meta is switching towards Creature based solutions and Elesh helps to shut them down. With Survival of the Fittest or Fauna Shaman and Elesh in hand, we can easily set her up by Tutoring for Loyal Retainers to cheat her onto the Battlefield. Once there, we can hard lock Opponents out of the game with the effect of Living Plane (provided they don't have copious amounts of Artifact based Mana). Elesh isn't the only Card to abuse this Enchantment either...
Linvala, Keeper of Silence: if you're in White and care about playing Stax... This is the one Card you should play. Not only does it shut down various Creature based win conditions, alongside Living Plane we cut off any Dork or Land based Mana our Opponents are using. However, Linvala alone is a huge enough threat to the board as it will require an answer regardless of her ability to work in tandem with other Stax elements we play. Also note, Loyal Retainers can grab her too.
Kataki, War's Wage: so many Legendary's to pull from and here's another! We've shut down their Lands and Dorks, so why not deprive them of their Artifacts? Kataki helps slow the progress of Artifact ramp lists by giving them an Upkeep Cost. It's essentially Tabernacle of Pendrell Vale, but for Artifacts. We run the bare minimum of Artifact ramp in this list because we're not reliant on it like so many others. With this benefit, we can punish those Artifact reliant lists with Kataki.
Leyline of the Void: is it enough to exile only their Creatures? No! Of course not. That's why we run this. 1. We won't always have Anafenza out and, 2. Fenza only cares about Creature strategies. Leyline of the Void dismisses any strategies that utilize the Graveyard that our Opponents might have. The operative word here being Opponents. It costs more than Rest in Peace with good reason. Oh, that is unless you start with it.
Living Plane: Outside of the aforementioned combos with Elesh Norn and Linvala, Living Plane serves a secondary purpose in making all our Lands Creatures. How is this beneficial? We need a certain threshold of Creatures to get the ball rolling with our reanimate strategy using Razaketh as he requires offerings for his Tutoring. If you're lacking the Creatures sufficient to Tutor with and combo out, this is the best way to get there (outside of Life / Death).