Cast any other instant and/or sorcery spell by paying its mana cost.
Holding priority, cast Teach by Example by paying {U/R}{U/R}, copying the next instant or sorcery spell you cast.
Cast Increasing Vengeance by paying {R}{R}, targeting the instant or sorcery spell cast in step 1.
Teach by Example triggers, copying Increasing Vengeance, with the copy targeting the original Increasing Vengeance.
Resolve the copy of Increasing Vengeance, copying Increasing Vengeance, with the copy targeting the original Increasing Vengeance.
Repeat step 5.

Infinite magecraft triggers

Teach by Example

Increasing Vengeance

Cast Teach by Example by paying {U/R}{U/R}, copying the next instant or sorcery spell you cast.
Cast Reality Spasm by paying at least {3}{U}{U}, targeting at least three permanents and choosing the untap mode.
Teach by Example triggers, copying Reality Spasm, targeting at least three permanents.
Holding priority, activate at least two mana-producing permanents you control by tapping them, adding at least {1}{U}.
Activate Errant by paying {1}{U} and tapping it, copying the Reality Spasm copy, targeting Errant and at least two mana-producing permanents you control.
Resolve the copy of Reality Spasm from step 3, untapping Errant and at least two mana-producing permanents you control.
Repeat from step 4.

Combos with "Teach by Example"