Activate all mana-producing nonland permanents you control by tapping them, adding at least {2}.
Activate Isochron Scepter by paying {2} and tapping it, causing you to cast a copy of the exiled instant.
Paradox Engine triggers, untapping all nonland permanents you control.
Resolve the copy of the instant.
Repeat.
If nonland permanents you control can tap to produce at least {3}, this combo nets infinite mana.

Infinite copies of cards exiled with Isochron Scepter

Infinite magecraft triggers

Infinite mana nonland permanents you control can produce

Infinite storm count

Infinite untap of nonland permanents you control

Paradox Engine

Isochron Scepter

Activate Witch's Oven by tapping it and sacrificing Metalwork Colossus, creating two Food artifact tokens.
Activate Metalwork Colossus by sacrificing the Foods, returning it from your graveyard to your hand.
Cast Metalwork Colossus by paying {0}.
Paradox Engine triggers, untapping all nonland permanents you control.
If applicable, activate any number of nonland permanents by tapping them, adding at least {1}.
Repeat.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Witch's Oven

Metalwork Colossus

Cast the spell, triggering Paradox Engine.
Tap Gilded Lotus for {3}.
Pay {2} and tap Strionic Resonator to copy the Paradox Engine trigger.
Resolve the copied Paradox Engine trigger.
Repeat from step 2 for infinite mana and nonland permanent untaps.

Infinite colored mana

Strionic Resonator

Gilded Lotus

Cast the spell, triggering Paradox Engine.
Tap Gilded Lotus for {3}.
Pay {2} and tap Lithoform Engine to copy the Paradox Engine trigger.
Resolve the copied Paradox Engine trigger.
Repeat from step 2 for infinite mana and nonland permanent untaps.

Lithoform Engine

Activate all mana-producing nonland permanents you control by tapping them, adding at least {1}{W}.
Cast Whitemane Lion by paying {1}{W}.
Paradox Engine triggers, untapping all nonland permanents you control.
When Whitemane Lion enters the battlefield, it triggers, returning itself from the battlefield to your hand.
Repeat.
If nonland permanents you control can tap to produce at least {2}{W}, this combo nets infinite mana.

Whitemane Lion

Activate all mana-producing nonland permanents you control by tapping them, adding at least {U}.
Cast Shrieking Drake by paying {U}.
Paradox Engine triggers, untapping all nonland permanents you control.
When Shrieking Drake enters the battlefield, it triggers, returning itself from the battlefield to your hand.
Repeat.
If nonland permanents you control can tap to produce at least {1}{U}, this combo nets infinite mana.

Shrieking Drake

Cast Summon the School for {3}{W}.
Paradox Egine triggers, untapping your nonlands permanents.
Tap your nonland permanents for at least {3}{W}.
Summon the School resolves, creating two 1/1 Merfolk tokens.
Tap 4 Merfolk you control to return Summon the School to your hand.
Repeat for infinite mana, storm, and merfolk tokens.

Infinite colorless mana

Infinite creature tokens

Summon the School

Cast Stonecloaker.
Paradox engine triggers untapping all our non-lands.
On resolution, Stonecloaker's ETB effects trigger, to preserve your own graveyard stack them as bounce, then exile, but to just exile all yards, order doesn't matter.
Tap all non-land mana sources for mana.
Responding to the exile trigger by casting Stonecloaker again allows you to repeat this process ad nauseum while only selecting a finite number of targets before letting the exile effects resolve.

Stonecloaker

Activate Priest of Yawgmoth by tapping and sacrificing Spine of Ish Sah, adding seven {B}.
Spine of Ish Sah triggers, returning itself from your graveyard to your hand.
Cast Spine of Ish Sah by paying {7}.
Paradox Engine triggers, untapping all nonland permanents you control.
Spine of Ish Sah enters the battlefield, destroying target permanent.
Repeat.

Destroy any number of target permanents opponents control

Near-infinite storm count

Mass Land Denial

Spine of Ish Sah

Priest of Yawgmoth

Sacrifice Urza's Bauble targeting any player.
Use Emry's ability targeting Urza's Bauble in graveyard.
Cast Urza's Bauble.
On ETB Paradox Engine triggers, untapping Emry and Sol Ring.
Tap Sol Ring for {C} {C}.

Urza's Bauble

Emry, Lurker of the Loch

Sol Ring

Cast Retraction Helix targeting Memnite Tap Sol Ring for {C} {C} Use Memnite's new ability to bounce Sol Ring to hand.
Cast Sol Ring triggering Paradox Engine untapping all nonland permanents.

Memnite

Retraction Helix

Cast Banishing Knack targeting Memnite Tap Sol Ring for {C} {C} Use Memnite's new ability to bounce Sol Ring to hand.
Cast Sol Ring triggering Paradox Engine untapping all nonland permanents.

Banishing Knack

Sacrifice Mishra's Bauble targeting any player.
Use Emry's ability targeting Mishra's Bauble in graveyard.
Cast Mishra's Bauble.
On ETB Paradox Engine triggers, untapping Emry and Sol Ring.
Tap Sol Ring for {C} {C}.

Combos with "Paradox Engine"