During the Damage Step, (ダメージステップ, Damējisuteppu) of the Battle Phase, the damage is calculated from the declared attack. If the defending monster is face-down, it is flipped face-up first during this Phase. If the defending monster has a Flip Effect, it is applied after Damage calculation, but still within the Damage Step. The Flip Effect does not affect monsters that have already been destroyed as a result of Damage Calculation. This includes the monster itself, so a flipped "Penguin Soldier" that was destroyed in battle cannot select itself as a target since it has already been destroyed. This is because, even though the monster has not left the field, it has already been decided that the "Penguin Soldier" in question will be sent to the Graveyard.
In the Damage Step, only certain cards and effects may be activated. These include:
- Spell/Trap Cards and card effects that directly alter the ATK/DEF of a monster(s).
- Note the use of "directly." You cannot perform an optional action that would only modify ATK/DEF indirectly, such as activating "Mystical Space Typhoon" that targets "Necrovalley", or activating "Reverse Trap".
- If the ATK/DEF modifier specifies Damage Step in its text, such as "Honest" or "Attack of the Cornered Rat", it can be activated up to, and including during damage calculation. If it doesn't specify Damage Step in its text and is optional, it can be used up to, but not including during damage calculation unless otherwise specified.
- Exceptions: If the trigger of an optional ATK/DEF modifying effect is a monster being Summoned to the opponent's side of the field, such as with "Armor Ninjitsu Art of Rust Mist" or "Evil Blast", the effect cannot be activated during the Damage Step. Also, "Scrap Sheen", "Zero Force", and "Curse of Anubis" cannot be activated during the Damage Step, as well as cards like "Half or Nothing" which might not alter ATK/DEF at resolution.
- Spell Speed 2 Monster Effects (Quick Effects) that negate the activation of something.
- Spell Speed 2 Monster Effects (Quick Effects) that must activate directly in response to an effect activation to negate the activated effect.
- You can activate the effects of "Photon Strike Bounzer", "Skull Meister", "Bujingi Turtle", etc.
- You cannot activate the effects of "Number 25: Force Focus", "Number 106: Giant Hand", etc.
- The difference is that cards like "Photon Strike Bounzer" or "Skull Meister" only negate one effect that is activating, and they must be activated directly in response to what they are negating. "Number 25: Force Focus" doesn't need to activate in direct response to an effect, and both it and "Number 106: Giant Hand" negate all effects, rather than the specific one that was activated.
- Any effect that specifically mentions an activation timing during the Damage Step.
- This is indicated by phrases in the text such as "During damage calculation," "At the start of the Damage Step," "After damage calculation," etc.
- Most Trigger Effects and Spell Card effects that trigger:
- Generally, effects of this nature are safe to activate during the Damage Step if they don't specifically state that you cannot.
- If the trigger of the effect is a monster being Summoned by the opponent or Summoned to the opponent's side of the field, such as "Catoblepas and the Witch of Fate" or "Naturia Horneedle", the effect cannot be activated in the Damage Step unless otherwise specified.
- An optional Trigger Effect of a monster to Special Summon itself from the hand cannot be activated in the Damage Step unless otherwise specified. This includes a monster like "Green Baboon, Defender of the Forest" whose effect has the potential to Summon itself from the hand or from another location, even if "Green Baboon of the Forest" is not actually in the hand.
- It is still suggested to look at every card in this category on a case-by-case basis.
- Cards that have no clear indication that they can be activated during the Damage Step, BUT have rulings stating that they are allowed to do so: "Attack and Receive", "Chthonian Blast", "Desrook Archfiend", "Null and Void", and "Numinous Healer".
At the end of the Damage Step, the Monster Card(s) destroyed by battle is sent to the Graveyard, unless an active card effect specifies that they go elsewhere, such as "Macro Cosmos" or "Grave Protector" is active.
- Breakdown of the Battle Phase (This page also includes a detailed breakdown of the Damage Step)