Sidisi, Brood Tyrant (EDH / Commander)

This is a well tuned graveyard synergy/value combo deck built around Sidisi, Brood Tyrant. Your normal game plan is to use a mixture of dredge pieces such as Dakmor Salvage, Life From the Loam and Golgari Grave Troll in combination with Greater Good, Sidisi, Brood Tyrant and Laboratory.

The basic premise is to use Greater Good to sacrifice a 2/2 zombie, then ideally Dredge 6 with Golgari Grave Troll, Dredge 3 with Life From the Loam and then discard 3 cards - each dredge effect should put a creature from your library in the graveyard, triggering Sidisi's ability, allowing for another zombie to enter the battlefield, continuing the cycle. Once you reach a state where you library is empty or almost empty, flashback Dread Return to bring back Laboratory Maniac, and sacrifice a zombie to Greater Good, forcing you to draw from an empty library. This cycel becomes even better with multiple creatures out, especially higher power ones, since Greater Good allows you to draw equal to the power of a creature. The Gitrog Monster massively accelerates this combo by allowing you draw, and thus dredge even more, on lands entering the graveyard as well. You have to be very careful not to become overzealous and accidentally draw from an empty library without Laboratory Maniac on the field, and as such this deck takes some getting used to when it comes to following all the triggers.

As a back-up plan we can use giant, high impact creatures such as Sheoldred, Whispering One, The Scarab God or Razaketh, Foulblooded to deal high amounts of evasive damage, or use Craterhoof Behemoth on a huge board for the classic token anthem kill.

This is notably expensive deck, mostly due to the land base and key pieces such as Survival of the Fittest, Doubling Season, Pact of Negation, Vampiric Tutor and Demonic Tutor, amongst others. These help to aid consistency and are not absolutely required to combo-off, so budget alternatives can absolutely work.

This isn't supposed to be a Tier 1 cEDH deck, although ti does use Hermit Druid, it cannot reliably tutor for and combo with it on Turn 3/4; nor is it a tribal zombie deck. Rather, it is a value Dredge deck with graveyard combos/synergies.

Notable includes:

Path of Discovery is absurd in this deck when paired with Sidisi, Brood Tyrant. Every time a creatures enters the battlefield the explore trigger either puts a land into hand, or a nonland into the graveyard. If this is a creature, which it is highly likely to be, we can choose to put that creature from our library into the graveyard, triggering Sidisi, Brood Tyrant, and putting another zombie onto the battlefield, triggering explore again - this cycle can continue for as long as you hit creatures, and every time it puts a zombie onto the battlefield with a +1/+1 counter on it, and the cycle can begin from just one creature entering the battlefield, including Sidisi, Brood Tyrant herself.

Ravnica Bounce-Lands:
these lands can at times be really bad, but here having to discard to hand-size on turn 2 allows us to Reanimate, or Animate Dead a huge target like Sheoldred, Whispering One on turn three, without needing both Reanimate and Entomb.

35 Lands:
To be honest, this is quite greedy and I would normally prefer more, but I think we can get away with it with the ramp and card draw we have.

Positives:
Multiple angles of attack
Consistency
Interactive
No two-card combos that instantly win the game
Can fight through STAX effects
Doesn't rely on its combo to win games

Negatives:
Folds to exile effects and graveyard hate
Easily disruptable combo
Long-winded process to win via Laboratory Maniac
Lots of stack triggers (not beginner friendly)
Expensive
Not reliant enough to be competitive in its current state