A plane that no longer moves. One side is completely frozen and the other is a hellish wasteland where the sun never sets.

Card Type Matters (not subtype, I'm talking the stuff Tarmogoyf cares about)

Starstill

Sorcery
If this is your first turn of the game, exile Starstill, then restart the game, except cards named Starstill that are in exile remain exiled. You are the first player in the restarted game. Otherwise, draw a card.

Starstill -
World Enchantment
When Starstill enters the battlefield, each player chooses a phase. (Phases are beginning, main precombat, combat, main postcombat and ending)
Skip your next turn: Choose a phase. Any player may play this ability, but only once each turn.
Players skip all phases that have not been chosen.

Starstill
Instant
This turn, each main phase and combat phase are replaced with an extra upkeep step.
The night seemed to last forever, then we realized a week had passed.

Okay. Let's do this.
:cracks fingers:
:jumps in place:
:talks himself up:
Okay.

...
Riorvard Interesting design space- making you go first. But it's only impactful in your starting hand, and then only if you're going 2nd.
...
Eph - Presents an appropriately agonizing choice. I like this. Not sure how it would really play out, but it is pretty cool.
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LilyStorm - Now that's something you don't see every... ever. Extra upkeeps? Phase replacement? I love the novel mechanic and the sheer Johnny factor, but it doesn't feel "Starstill". I guess it's disruptive and has a "wear of time" feel, but I'd like it more under a different name. 3 extra upkeeps could do crazy things. Or you just Fog + Silence them.
...
I choose EPH
Would like if the card offed itself once the last step is chosen though.
Does skipping end phase remove the cleanup step? I think that's its own thing.