Cast any instant or sorcery spell.
Holding priority, cast Increasing Vengeance for its flashback cost by paying {3}{R}{R}.
Sevinne triggers, creating a copy of Increasing Vengeance, targeting Increasing Vengeance.
Resolve the copy of Increasing Vengeance, creating a copy of Increasing Vengeance, targeting Increasing Vengeance.
Repeat step 4.

Infinite magecraft triggers

Sevinne, the Chronoclasm

Increasing Vengeance

Cast any instant or sorcery spell.
Holding priority, cast Cooperate from your graveyard by paying {2}{U}.
Sevinne triggers, creating a copy of Cooperate, targeting Cooperate.
Resolve the copy of Cooperate, creating a copy of Cooperate, targeting Cooperate.
Repeat step 4.

Refuse // Cooperate

Cast the spell in your hand.
In response cast Increasing Vengeance from your graveyard to copy it.
Sevinne, the Chronoclasm's ability triggers copying Increasing Vengeance.
Copy the original Increasing Vengeance.
Repeat.
For each copy made Ral, Storm Conduit will trigger dealing 1 damage to an opponent.

Infinite damage

Ral, Storm Conduit

Cast the spell in your hand.
In response cast Refuse // Cooperate from your graveyard to copy it.
Sevinne, the Chronoclasm's ability triggers copying Refuse // Cooperate.
Copy the original Refuse // Cooperate.
Repeat.
For each copy made Ral, Storm Conduit will trigger dealing 1 damage to an opponent.

Combos with "Sevinne, the Chronoclasm"