At first glance, this deck looks unoptimized. And yeah, it probably is. It doesn't even have a real win condition, or even any way to threaten the opponent. But since you're not the one who's stuck using it, that's not a problem.
The goal of this deck is to switch decks with the opponent through Shared Fate. This can be done as soon as turn 3, with Pentad Prism. After a couple of Thoughtseizes and Dreadbores, the path should be mostly clear.
Since your opponent is going to be using your cards as much as you're using theirs, there are some specific effects to avoid putting into this deck. First is enchantment removal: if your Shared Fate gets destroyed, you're back to using the garbage deck. Next is tutor effects, which let the opponent search their own library for the cards they need. Last is player damage/life loss; there are lots of ways to kill creatures without finding yourself on the wrong end of your own Lightning Bolt.
Conversely, there are effects that are generally safe, like discard, removal for everything except enchantments, and graveyard abilities. Discard helps you control the match until you get to the switch, and doesn't affect you after the switch. Non-enchantment removal has a similar role before switching, and this deck has a low permanent count. Finally, if your opponent tries to get value out of a Kroxa, Titan of Death's Hunger, Cut / Ribbons, or Echo of Eons, it goes to your graveyard after resolving so you can take advantage of it safely.
Interestingly, buyback effects like Mystic Speculation return to their owner's hand on resolving, so that's another avenue to take advantage of. If you cast it after Shared Fate is out, you can stack your deck to prevent your opponent from getting anything useful.
Points I'm still working on:
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how much card draw and scry to include
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whether land destruction and counterspells are safe
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land base: are cycling lands safe? Are they better than scrylands? Are shocklands better or worse?
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sideboarding
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individual cards like Grim Reminder
(Add cycling, per Angel_Zero's deck here).
