Can you activate a card effect that reads per outside of your Main Phase in Yu-Gi-Oh?

It depends on the specific card effect. Some effects are limited to specific phases, like "during your Main Phase," while others don't specify a phase.

Here's a breakdown:

* Effects that specifically require a Main Phase: You can only activate these effects during your Main Phase.

* Effects that specify another phase: You can only activate these effects during the specified phase (e.g., during your Standby Phase, during your opponent's turn).

* Effects with no phase restriction: You can activate these effects outside of your Main Phase as long as the other activation conditions are met (e.g., the card is on the field, you have the required resources, etc.).

Examples:

* "Activate this effect during your Main Phase." You can only activate this effect during your Main Phase.

* "During your Standby Phase, you can add 1 card from your Deck to your hand." You can only activate this effect during your Standby Phase.

* "You can discard 1 card to inflict 500 damage to your opponent." This effect doesn't specify a phase, so you can activate it outside of your Main Phase.

Remember: Always read the card text carefully to determine the activation requirements. If it doesn't specify a phase, you can generally activate it outside of your Main Phase. However, there might be other restrictions, such as timing, cost, or target selection.