The Doomsday Machine (EDH / Commander)

This deck can go infinite in a bunch of different ways, as long as Teshar is out.

Fundamentally what we want is a sac outlet, a free creature and an artifact returner. Some of these require mana (which is fine as long as the sac outlet is Ashnod's Altar) but most don't.

With this combo, we can cycle infinitely. It varies slightly depending on how the returner works (Trusty Packbeast works on ETB, Myr Retriever works on death for example), but with it in our graveyard, we play our free creature and bring back our returner, sac our free creature (in response if required) and use our retriever (either ETB or death) to get the free creature back, then repeat infinitely.

Once we have this loop, there are many ways we can take advantage of it.

Mill everyone if the sac outlet is Altar of Dementia.
Gain infinite life from Impassioned Orator.
Create infinite tokens from Oketra's Monument and Desecrated Tomb.
Drain everyone to death from Bontu's Monument.
Infinite mana with Ashnod's Altar.

If you have your cost reducers out too you can make something infinitely big with Sparring Construct.

Before the Doomsday Machine is assembled, you have a huge amount of value recursion in your creatures to help see you into the long game. This can also provide a lot of consequential value. Draw cards from Filigree Familiar and Skyscanner. Gain life from Filigree Familiar and Bottle Gnomes (who are lowkey great here. All of you historic spells basically now also have "Gain 3 life" on them too). A little bit of control from the likes of Aven Mindcensor, Fiend Hunter and Fairgrounds Warden.

Potential Future Upgrades:
Swords to Plowshares
Expedition Map
Smothering Tithe