Edison Rules Compendium

Damage Step

Once the Damage Step has been entered, only the following cards/effects may be activated.
This list of cards is rather convoluted, so here is a neat acronym to help:

S - Spell Speed 3

Counter Trap Cards (as they are Spell Speed 3) may be activated at any point in the Damage Step, even during Damage Calculation.

A - Activation Negation

Monster effects (but not Spell/Trap cards) which negate the activation or effect of cards/effects may be activated at any point in the Damage Step, even during Damage Calculation.

N - Non-optional (mandatory) effects

Mandatory Effects (as they must always activate when possible) may be activated at any point in the Damage Step, even during Damage Calculation.

T - Trigger Effects (if the card itself is moving location)

Any Trigger effect which is activated as part of the card itself moving location (or being flipped face-up, or changing battle position) may be activated, but not during Damage Calculation. This includes things like:

• Flip Effects or monster effects which happen when being flipped face-up,
• “Green Gadget" being Summoned by the effect of “Giant Rat",
• “Dupe Frog" being destroyed by battle.

A - ATK/DEF Modifiers

Fast Effects which directly alter ATK/DEF may be activated, but not during Damage Calculation, unless they can be activated “During the Damage Step“, like that of "Honest" or “Blackwing - Kalut the Moon Shadow".