Cast Temporal Extortion by paying {B}{B}{B}{B}.
Temporal Extortion and Aetherflux Reservoir trigger.
Resolve the Aetherflux Reservoir trigger, causing you to gain 1 life for each spell you've cast this turn.
Resolve the Temporal Extortion trigger, causing you to pay half your life total, rounded up, and then exile Temporal Extortion and cast it without paying its mana cost due to Guile.
Repeat.
Once you have infinite life, you may activate Aetherflux Reservoir infinite times to deal infinite damage to any target(s).

Infinite damage

Infinite lifegain

Infinite lifegain triggers

Infinite lifeloss

Infinite magecraft triggers

Infinite storm count

Guile

Temporal Extortion

Aetherflux Reservoir

Cast Temporal Extortion by paying {B}{B}{B}{B}.
Temporal Extortion and Professor Onyx trigger.
Resolve the Temporal Extortion trigger, causing you to pay half your life total, rounded up, and then exile Temporal Extortion and cast it without paying its mana cost due to Guile.
Repeat from step 2 until your life total is four or less.
Temporal Extortion and Professor Onyx trigger.
Resolve the Professor Onyx trigger, causing you to gain two life and each opponent to lose 2 life.
Resolve the Temporal Extortion trigger, causing you to pay half your life total, rounded up, and then exile Temporal Extortion and cast it without paying its mana cost due to Guile.
Repeat from step 5.

Professor Onyx

Activate Kuro by paying 1 life, targeting any creature not used for this combo.
Holding priority, repeat the previous step until you have 1 life remaining.
Resolve all Kuro abilities.
Cast Repay in Kind by paying {5}{B}{B}, causing all life totals to become 1.
Cast Temporal Extortion by paying {B}{B}{B}{B}.
If an opponent pays 1 life to counter it, that opponent's life total becomes 0, they lose the game, and you skip the next step.
Otherwise, resolve Temporal Extortion, gaining an extra turn.
Activate Canal Dredger by tapping it, putting Temporal Extortion from your graveyard on the bottom of your library.
Declare Varragoth as an attacker.
Activate Varragoth's Boast ability by paying {1}{B}, searching your library for Temporal Extortion and putting on top of your library.
Go to your next turn.
Draw Temporal Extortion in your draw step.
Repeat from step 7.

On each of your turns, you take an extra turn unless an opponent chooses to lose the game

Lock

Varragoth, Bloodsky Sire

Kuro, Pitlord

Repay in Kind

Canal Dredger

Cast Temporal Extortion by paying {B}{B}{B}{B}.
Temporal Extortion and Mirari trigger.
Resolve the Mirari trigger, paying {3} and copying Temporal Extortion.
Resolve the Temporal Extortion copy, causing you to take an extra turn after this one.
Resolve the Temporal Extortion trigger, allowing any player to pay half their life to counter the spell.
If no one does, resolve Temporal Extortion, causing you to take an extra turn after this one.
Activate Canal Dredger by tapping it, putting Temporal Extortion on the bottom of your library.
Declare Varragoth as an attacker.
Pay {1}{B} to activate Varragoth, searching your library for Temporal Extortion and putting it on top.
Repeat each turn.

Infinite turns

Mirari

Cast Temporal Extortion for {B}{B}{B}{B}.
Temporal Extortion triggers, allowing any player to pay half of their life to counter the spell.
Pay half of your life to counter Temporal Extortion, exiling it and allowing you to cast it without paying its mana cost.
Repeat steps 2-3 until you have one life remaining and the Temporal Extortion trigger is on the stack.
Choose not to pay half of your life to counter Temporal Extortion, allowing it to resolve.
If any of your opponent choose to pay half of their life to counter the spell, Guile will exile it and allow you to cast it again.
Repeat steps 5-6 until none of your opponent choose to counter Temporal Extortion.
Move to the upkeep step of your extra turn.
Near-Death Experience triggers, winning you the game.

Win the game

Near-Death Experience

Activate Unspeakable Symbol as many times as possible by paying all but 1 life, putting +1/+1 counters on creatures you control Cast Repay in Kind by paying {5}{B}{B}, causing all life totals to become 1.
Cast Temporal Extortion by paying {B}{B}{B}{B}.
If an opponent pays 1 life to counter it, that opponent's life total becomes 0, they lose the game, and you skip the next step.
Otherwise, resolve Temporal Extortion, gaining an extra turn.
Activate Canal Dredger by tapping it, putting Temporal Extortion from your graveyard on the bottom of your library.
Declare Varragoth as an attacker.
Activate Varragoth's Boast ability by paying {1}{B}, searching your library for Temporal Extortion and putting on top of your library.
Go to your next turn.
Draw Temporal Extortion in your draw step.
Repeat from step 7.

Unspeakable Symbol

Cast Temporal Extortion by paying {B}{B}{B}{B}.
Temporal Extortion and Witherbloom Apprentice trigger.
Resolve the Temporal Extortion trigger, causing you to pay half your life total, rounded up, and then exile Temporal Extortion and cast it without paying its mana cost due to Guile.
Repeat from step 2 until your life total is equal to one.
Temporal Extortion and Witherbloom Apprentice trigger.
Resolve the Witherbloom Apprentice trigger, causing you to gain 1 life and each opponent to lose 1 life.
Resolve the Temporal Extortion trigger, causing you to pay half your life total, rounded up, and then exile Temporal Extortion and cast it without paying its mana cost due to Guile.
Repeat from step 5.

Combos with "Temporal Extortion"