Cast any other instant or sorcery by paying its mana cost, triggering Arcane Bombardment.
Holding priority, cast Return the Favor by paying {R}{R} and then choosing to pay an additional {1} to select its first mode, copying the Arcane Bombardment trigger.
Resolve the copy of the Arcane Bombardment trigger, exiling Return the Favor from your graveyard and then copying Return the Favor, Prismari Command and all other cards exiled by Arcane Bombardment, and allowing you to cast those copies without paying their mana costs.
As you cast the Return the Favor copy, choose to pay an additional {1} to select its first mode, targeting the Arcane Bombardment trigger.
Resolve the copy of Prismari Command, creating a Treasure token and choosing any other mode.
Activate the Treasure by tapping and sacrificing it, adding {1}.
Resolve the copy of Return the Favor, copying the Arcane Bombardment trigger.
Repeat from step 3.

Infinite damage

Infinite storm count

Infinite magecraft triggers

Infinite draw triggers for any number of players

Infinite looting for any number of players

Infinite self-discard triggers for any number of players

Arcane Bombardment

Prismari Command

Return the Favor

Cast Inspiring Refrain by paying {4}{U}{U}.
Arcane Bombardment triggers, exiling a random instant or sorcery from your graveyard, and then casting a copy of Time Stretch without paying its mana cost.
Resolve the Time Stretch copy, causing you to take two extra turns after this one.
Resolve Inspiring Refrain, causing you to draw two cards and exile Inspiring Refrain with three time counters on it.
Activate Jhoira's Timebug by tapping it, removing a time counter from Inspiring Refrain.
Move to your first extra turn, removing a time counter from Inspiring Refrain during your upkeep.
Move to your second extra turn, removing a time counter from Inspiring Refrain during your upkeep.
Inspiring Refrain triggers, causing you to cast it from exile without paying its mana cost.
Repeat from step 2.

Infinite turns

Lock

Inspiring Refrain

Jhoira's Timebug

Time Stretch

Cast Clockspinning with buyback by paying {3}{U}.
Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Time Warp without paying its mana cost.
Resolve Time Warp, causing you to take an extra turn after this one.
Resolve Clockspinning, returning Clockspinning to your hand.
Repeat each turn.

Time Warp

Clockspinning

Cast Clockspinning with buyback by paying {3}{U}.
Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Temporal Manipulation without paying its mana cost.
Resolve Temporal Manipulation, causing you to take an extra turn after this one.
Resolve Clockspinning, returning Clockspinning to your hand.
Repeat each turn.

Temporal Manipulation

Cast Mystic Speculation with buyback by paying {2}{U}.
Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Time Warp without paying its mana cost.
Resolve Time Warp, causing you to take an extra turn after this one.
Resolve Mystic Speculation, causing you to scry 3 and return Mystic Speculation to your hand.
Repeat each turn.

Mystic Speculation

Cast Mystic Speculation with buyback by paying {2}{U}.
Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Temporal Manipulation without paying its mana cost.
Resolve Temporal Manipulation, causing you to take an extra turn after this one.
Resolve Mystic Speculation, causing you to scry 3 and return Mystic Speculation to your hand.
Repeat each turn.

Cast Inspiring Refrain by paying {4}{U}{U}.
Arcane Bombardment triggers, exiling a random instant or sorcery from your graveyard, and then casting a copy of Temporal Manipulation and Time Warp without paying their mana costs.
Resolve the Temporal Manipulation and Time Warp copies, causing you to take two extra turns after this one.
Resolve Inspiring Refrain, causing you to draw two cards and exile Inspiring Refrain with three time counters on it.
Activate Jhoira's Timebug by tapping it, removing a time counter from Inspiring Refrain.
Move to your first extra turn, removing a time counter from Inspiring Refrain during your upkeep.
Move to your second extra turn, removing a time counter from Inspiring Refrain during your upkeep.
Inspiring Refrain triggers, causing you to cast it from exile without paying its mana cost.
Repeat from step 2.

Cast Whim of Volrath with buyback by paying {2}{U}.
Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Time Warp without paying its mana cost.
Resolve Time Warp, causing you to take an extra turn after this one.
Resolve Whim of Volrath, returning Whim of Volrath to your hand.
Repeat each turn.

Whim of Volrath

Cast Whim of Volrath with buyback by paying {2}{U}.
Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Temporal Manipulation without paying its mana cost.
Resolve Temporal Manipulation, causing you to take an extra turn after this one.
Resolve Whim of Volrath, returning Whim of Volrath to your hand.
Repeat each turn.

Combos with "Arcane Bombardment"