Tap Scroll Rack and pay {1} to activate it, putting Temporal Mastery on top of your library.
Pass the turn.
On your next draw step, when you draw Temporal Mastery, reveal it due to Kefnet's ability, making a copy that costs {2} less to cast.
Cast the copy for {3}{U}{U}, granting you an extra turn.

Infinite turns

Skip your draw step

God-Eternal Kefnet

Scroll Rack

Temporal Mastery

At the beginning of your upkeep, Panoptic Mirror triggers, casting a copy of Temporal Mastery without paying its mana cost.
Resolve Temporal Mastery, causing you to take an extra turn after this one.
Repeat each turn.

Panoptic Mirror

Activate Jace's zero loyalty ability, putting Temporal Mastery on top of your library.
Pass the turn.
On your next draw step, when you draw Temporal Mastery, reveal it due to Kefnet's ability, making a copy that costs {2} less to cast.
Cast the copy for {3}{U}{U}, granting you an extra turn.

Jace, the Mind Sculptor

Cast the self-suspending card by paying its mana cost if its in your hand, or any other spell otherwise if you have not cast a spell this turn.
Cast Temporal Mastery by paying its mana cost.
Taigam triggers, copying Temporal Mastery and then exiling it with four time counters on it and giving it suspend.
Resolve the copy of Temporal Mastery, causing you to take an extra turn after this one.
Move to your next turn. At the beginning of that turn's upkeep, Temporal Mastery and the self-suspending card's suspend abilities trigger, removing a time counter from each of them.
Activate The Tenth Doctor by paying {7}, removing three time counters from Temporal Mastery and the self-suspending card, triggering their suspend abilities.
Resolve the self-suspending card's suspend trigger, causing you to cast it from exile without paying its mana cost, and eventually exile it with time counters on it.
Resolve the Temporal Mastery's suspend trigger, causing you to cast it from exile without paying its mana cost.
Repeat from step 3.

Self-Suspending Instant or Sorcery

The Tenth Doctor

Taigam, Master Opportunist

Cast Temporal Mastery by paying {5}{U}{U}.
Riku's first ability triggers - choose not to pay.
Holding priority, cast Narset's Reversal by paying {U}{U}, targeting Temporal Mastery.
Riku's first ability triggers, causing you to pay {U}{R} to copy Narset's Reversal, with the copy targeting the original Narset's Reversal.
Resolve the copy of Narset's Reversal, copying the original Narset's Reversal targeting Temporal Mastery, and returning the original Narset's Reversal to your hand.
Resolve the copy of Narset's Reversal created in step 5, copying Temporal Mastery and returning the original Temporal Mastery to your hand.
Resolve Temporal Mastery, causing you to take an extra turn after this one.
Repeat each turn.

Riku of Two Reflections

Narset's Reversal

Cast Temporal Mastery by paying {5}{U}{U}.
Saheeli triggers, creating a 1/1 Servo artifact creature token.
Resolve Temporal Mastery, causing you to take an extra turn after this one and exile it.
Activate Saheeli by removing two loyalty counters from it, causing the Servo to become a copy of Mirror of Fate until end of turn.
Activate the Servo by tapping and sacrificing it, choosing Temporal Mastery and up to six other cards face up in exile, then exiling your library and putting the chosen cards on top of your library, with Temporal Mastery being the top most card.
If Saheeli has less than three loyalty counters on it, activate Venser's first loyalty ability by putting two loyalty counters on it, exiling Saheeli until your next end step.
At the beginning of your end step, if you activated Venser's ability, Venser triggers, returning Saheeli from exile to the battlefield.
Move to your next turn, drawing Temporal Mastery during your draw step.
Repeat.

Saheeli, Sublime Artificer

Venser, the Sojourner

Mirror of Fate

Activate Mirror of Fate by tapping and sacrificing it.
Holding priority, activate Scrabbling Claws by tapping it, causing you to exile Mirror of Fate from your graveyard.
Resolve the Mirror of Fate ability, choosing itself, Temporal Mastery and three to five other cards, then exiling your library and putting the chosen cards on top, ensuring Temporal Mastery and Mirror of Fate are the topmost cards.
Declare Narset as an attacker.
Narset triggers, exiling the top four cards of your library and allowing you to cast them from exile this turn without paying their mana costs.
Move to your postcombat main phase.
Cast Temporal Mastery from exile without paying its mana cost, causing you to take an extra turn after this one and exile Temporal Mastery.
Cast Mirror of Fate from exile without paying its mana cost.
Repeat each turn.

Narset, Enlightened Master

Scrabbling Claws

Declare Fire Lord Azula as an attacker, triggering its firebending ability, adding {R}{R}.
Holding priority, cast Temporal Mastery by paying its mana cost.
Fire Lord Azula's second ability triggers, copying Temporal Mastery.
Holding priority, cast Narset's Reversal by paying {U}{U}, targeting the original Temporal Mastery spell.
Fire Lord Azula's second ability triggers, copying Narset's Reversal, targeting the original Narset's Reversal.
Resolve the copy of Narset's Reversal, causing you to copy Narset's Reversal targeting the original Temporal Mastery spell, and then return the original Narset's Reversal to your hand.
Resolve the copy of Narset's Reversal, copying Temporal Mastery and returning the original Temporal Mastery to your hand.
Resolve both copies of Temporal Mastery from steps 3 and 7, causing you to take two extra turns after this one.
Repeat during your second extra turn.

Fire Lord Azula

Vedalken Orrery

Cast Temporal Mastery by paying {5}{U}{U}, taking an extra turn after this one.
Activate Mirror of Fate by tapping and sacrificing it, choosing Temporal Mastery from exile and putting it on the top of your library.
Cast Mirror of Fate from your graveyard by paying {5}.
Move to your next turn.
Cast Temporal Mastery for its miracle cost by paying {1}{U}.
Repeat from step 2.

Muldrotha, the Gravetide

Cast the extra turn spell and move to your extra turn.
Activate Isochron Sceptre to cast Pull from Eternity, putting the extra turn spell from exile to your graveyard.
Attack with Backdraft Hellkite to give your extra turn flashback, then cast it.
Repeat for infinite turns.

Isochron Scepter

Pull from Eternity

Backdraft Hellkite

Cast Temporal Mastery by paying its mana cost.
Taigam triggers, copying Temporal Mastery and exiling the original Temporal Mastery with four time counters on it.
Resolve the Temporal Mastery copy, causing you to take an extra turn after this one.
Cast Clockspinning with buyback by paying {3}{U}, removing a time counter from Temporal Mastery and returning Clockspinning to your hand.
Repeat step 4 one additional time.
Move to your next turn. At the beginning of your upkeep, Temporal Mastery's suspend ability triggers, removing a time counter from it.
Cast Clockspinning with buyback by paying {3}{U}, removing a time counter from Temporal Mastery and returning Clockspinning to your hand.
Temporal Mastery's suspend ability triggers, causing you to cast it from exile without paying its mana cost.
Repeat from step 2.

Taigam, Master Oppurtunist

Clockspinning

Cast Temporal Mastery by paying {5}{U}{U}.
Saheeli triggers, creating a 1/1 Servo artifact creature token.
Resolve Temporal Mastery, causing you to take an extra turn after this one and exile it.
Activate Contagion Engine by paying {6} and tapping it, putting two loyalty counters on Saheeli.
Activate Saheeli by removing two loyalty counters from it, causing the Servo to become a copy of Mirror of Fate until end of turn.
Activate the Servo by tapping and sacrificing it, choosing Temporal Mastery and up to six other cards face up in exile, then exiling your library and putting the chosen cards on top of your library, with Temporal Mastery being the top most card.
Move to your next turn, drawing Temporal Mastery during your draw step.
Repeat.

Contagion Engine

Deal combat damage to an opponent using Efreet Flamepainter.
Efreet Flamepainter triggers, causing you to cast Temporal Mastery from your graveyard without paying its mana cost.
Resolve Temporal Mastery, causing you to take an extra turn after this one and exile it.
Activate Isochron Scepter by paying {2} and tapping it, casting a copy of Pull from Eternity without paying its mana cost.
Resolve Pull from Eternity, putting Temporal Mastery from exile into your graveyard.
Repeat each turn.

Efreet Flamepainter

Cast Temporal Mastery by paying {5}{U}{U}, causing you to take an extra turn after this one and exile Temporal Mastery.
Activate Isochron Scepter by paying {2} and tapping it, casting a copy of Pull from Eternity without paying its mana cost.
Resolve Pull from Eternity, putting Temporal Mastery into your graveyard from exile.
Move to your next turn.
Activate Dralnu by tapping it, giving Temporal Mastery flashback until end of turn.
Cast Temporal Mastery from your graveyard by paying {5}{U}{U}, causing you to take an extra turn after this one and exile Temporal Mastery.
Repeat from step 2.

Dralnu, Lich Lord

Cast Temporal Mastery by paying {5}{U}{U}, causing you to take an extra turn after this one and exile Temporal Mastery.
Activate Isochron Scepter by paying {2} and tapping it, casting a copy of Pull from Eternity without paying its mana cost.
Resolve Pull from Eternity, putting Temporal Mastery into your graveyard from exile.
Move to your next turn.
Cast Temporal Mastery from your graveyard by paying {5}{U}{U}, causing you to take an extra turn after this one and exile Temporal Mastery.
Repeat from step 2.

Combos with "Temporal Mastery"