When I first started playing commander in 2009, I build a monoblack removal/discard heavy deck with Nezumi Graverobber // Nighteyes the Desecrator as the commander without realizing this wasn't a legal option. General plan was proactively get my opponent's creatures in their graveyards for me to use. Queue Mirroden Besieged and Geth, Lord of the Vault being printed. That swap brought my focus to be less on reanimating my own creatures, but Geth can feed his own ability by milling opponents. He is also a wincon with sufficient mana, and not even eldrazi titans reshuffling can prevent it if they're on my battlefield.
The general strategy and play pattern of the deck is fairly straightforward. Build a mana heavy board state while playing board control, and eventually land Geth to start transitioning mana production into value engines and winconditions. I call this suicide control because it's fairly open to attack in the early game, and when combined with using life as a resource, it is not uncommon to be down most of your starting life total with a Pestilence in play.
Edited from here to add more detail on strategy and card choices.
Late game finishers include several combos:
- Infinite turns or 1 opponent dead/turn with Temporal Extortion + Wound Reflection recurred with Xiahou Dun, the One-Eyed. With 10 mana, leading out extortion with mana up for the wound reflection is a bluff for each opponent.
- Infinite mana from a mass mana land like Cabal Coffers with Deserted Temple and Rings of Brighthearth.
- Repeated recursion of Gray Merchant of Asphodel with Chainer, Dementia Master or Nim Deathmantle and a sacrifice outlet
- Mind Slash, Infernal Tribute, and Phyrexian Arena are of specific note because they avoid a large number of my own board wipes by being enchantments, while also being extremely devotion heavy to help get Nykthos, Shrine to Nyx online. They are also targets for Xiahou Dun, the One-Eyed for recursion. I can play these early without much worry and they set up well for mid/late game.
- Mind Slash specifically, while sorcery speed only, is a repeatable method to get information from opponent's hand while placing targets that I want for Geth and removing counterspells or other stack control pieces.
- Infernal Tribute is a sacrifice outlet for any card, which is relevant when Geth can target artifacts. Generally, this makes most mana rocks into Mind Stone at the worst. With Amulet of Vigor in play, an opponent's Sol Ring becomes : draw a card.
- Phyrexian Arena is emblematic of my card advantage in this deck. Frankly, I don't run much of it. This is primarily because I intend the largest source of cards and value to be from my opponents. What dedicated card advantage I run all performs a secondary role, often removal in some form.
- Amulet of Vigor is entirely there to support Geth by untapping mana rocks or blockers when I steal them. This significantly helps when try not to die to attackers.
- Nevinyrral's Disk can enter untapped with Amulet, which greatly improves it's value. If there were a comparable board wipe without the semi-random nature of Boompile, I'd swap it.
- All my sacrifice outlets need to be both good for value over turns or multi-use in a single turn. If I have enough mana to mill somone out, but they are playing spellslinger with very few Geth targets, the sacrifice outlets are needed to close the game out.
- NOT including Sanguine Bond or similar to pair with Exquisite Blood for both style reasons and because there is very little life gain.