* Activation Timing: "Breaker the Magical Warrior" is a Continuous Spell card. Continuous Spells are typically activated during your Main Phase. They have persistent effects that last for the duration of the Duel.
* Opponent's Turn Restrictions: The game rules restrict you from activating most card effects during your opponent's turn. There are some exceptions, like trap cards and monster effects that specifically allow activation on the opponent's turn.
In summary: You can only activate "Breaker the Magical Warrior" during your Main Phase, not during your opponent's turn.