What does 'during damage calculation only' mean in Yu-Gi-Oh?

Answer 1

When monsters attack during the Battle Phase, there are actually multiple "steps" that take place. When a player declares an attack, you enter the "Battle Step". If no card effects are activated that would stop the attack, you enter the "Damage Step" in which face-down monsters are flipped face-up and you actually calculate how much damage is done. It's at this point that a card that reads "during damage calculation only" can be activated or takes effect.

For more information on how card effects can work and activate during the Battle Phase, refer to the Related Links section below.