**This list is preliminary and will take some time to get down to 99... a lot of cards will be added/removed, and some, if lucky, will make it to the Maybeboard list as backup options, which also includes some high synergy cards that cost ~$10+.

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I don't think this deck needs too much explanation... it's a build that's purposely limited to $100 (play group challenge), and it's primarily filled with creatures that ETB with +1/+1 counters natively, and that have death or ETB triggers, plus a bunch of sac outlets and other cards with death triggers.  Add in Marchesa and you can sacrifice creatures that ETB with +1/+1 counters on each player's turn, bringing them back at the end as untapped blockers for the next turn, then rinse and repeat.  Any creatures that don't naturally put +1/+1 counters on themselves will have to attack and use dethrone to gain Marchesa's recursion protection, but that's not too big of an issue.  Having your creatures ETB with +1/+1 counters also alleviates your need to abuse dethrone and primarily attack the player with the most life, which will change the dynamic of how everyone else reacts to your shenanigans.  And being able to attack anyone you want lets you dictate your own game plan better.

The biggest question of a build like this is where to put your money...?  First, it's important to recognize how cheap this deck can be built with high synergy cards that do a lot in tandem with Marchesa, but are very cheap to buy.  That being said, Marchesa is tri-color, and the better the lands, the faster the deck, so I'm thinking that's my focus: build cheap and efficient everywhere else and invest in the lands.  It already has enough good ramp and draw to explode cards out, so a solid mana base that can ETB untapped could make it a lot more competitive.  If you wanted, you could certainly go cheaper on lands and swap a few cards into other slots that cost more, and help the deck more.  It's up to you.

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Jar of Eyeballs is sneaky good in here, primarily because it lets you put all the cards you looked at on the bottom of your library in any order.  Say you have 80 cards left in your library... you need to have creatures you control die 40 times, which sounds like a lot, but with four players if you sacrifice five creatures on each player's turn (which isn't a far-fetched reality), after two complete rounds of turns you'll have forty counters on the Jar.  Four crits a turn will get you there in three rounds of turns.  Then you're reorganizing your whole library.  And you aren't sacrificing the Jar, so you can potentially use it again if someone forces you to shuffle your library.

Prowling Geistcatcher requires a complimentary creature token engine to be able to keep putting +1/+1 counters on it, but if you can sac a creature token on each player's turn you can use Geistcatcher to get two sac/death/ETB triggers per creature by sacrificing the Geistcatcher after all your other creatures, which he then brings back when you sac him, then sac all those creatures again, all in the second main phase, then get them back again at the end of the turn.  But if you cast him before you have a token engine, you're kinda screwing yourself, forcing yourself to sac him only on your turns when you can attack and put a counter on him from Marchesa, preventing them from being available to be sacrificed on each player's turn.  Or just sac him and let him go to the grave.  In this deck, he's got a real Dr. Jekyl and Mr. Hyde complex.