Ikoria asks us some pretty difficult questions as the modern mill player. The small ball upgrades are interesting. Triome's improve our greedy manabase, particularly the sultai triome, which is an island and a functional watery grave on top of producing green. The second may also be a consideration depending on much we want to go into white. Cycling isn't strictly un-usuable in this deck either, this may inflate our land count. This should make our fourth color splash much easier.  Boon of the wish-giver is an interesting comparison to the now incredible into the story. It might not beat it on rate, but a 1 mana cantrip that also is a draw four is pretty good, a mid ground between visions and story. Still, I think story is just likely better. Shark typhoon is another effect in the creature spell library, and might be a considerable option.

The big question though is what companion are we going to use? Because using one is not optional. having access to an eighth card at all times is just too good of an effect to pass up for as long as they are available. Your list has to be pretty hardcore locked in not to include a free eighth card in every game. We can play Umoori, Lurrus, the orphanguard, Zirda, and Yorion without much effort in deck adjustment. Umoori and zirda have some impact but mostly seem like just a body.

The orphanguard is literally free and vigilance ain't bad, as well as being 3 cmc. I can see it on offense and defense, helping with our planeswalker issue a bit, and punishing our opponent both ways for leaving in or taking out removal. This also might be the least card slots for high impact, as it is one side board card, and I can include white sun's zenith as a 1 of maindeck. Makes cat tokens! This can be much like a cat fireball at instant speed, an effect I already liked the idea of for the deck, and an angle that decks should just not be able to switch on easily.

Lurrus is the highest value option, but probably the most deck warping, as a playset of Mishra bauble's at the very least seems like a sound idea. Lifelink is great, and this Lurrus is likely looping EE and nodes (EE can get to 4 easily by the way now), basically punishing other Lurrus decks. It also pushes us back to hedron crabs.

Yorion is a fine body, likely comes with astrolabes and other cantrips, a fine outlet to have. Makes the deck bigger, which I just fundamentally can't get behind. I want more archive traps, not less. And I definitely wouldn't be the best Yorion.

Following this I have to consider how to play against companions. Countering them seems strong, and maindeck kaya's guile and surgical extraction is pretty great against Lurrus. The biggest hurdle I think is actually the deckbuilding requirement of Torion decks. With a bunch of 80 card decks running around, I now have to have an 80 card mill plan, or acute angles of attack. Can I beat 80 card Yorion control decks? Do they have game against a straight control deck?