∵toughness功能在assign damage步骤生效cancel damage
(rule book P16：……Whenever a unit with the Toughness keyword is assigned
damage, the Toughness keyword cancels its numeric value of that damage before the damage is applied. ……）
∴只要damage有assign步骤，toughness就可以生效cancel damage
∵Indirect Damage is non-combat damage that is dealt to a target player. （FAQ1.1 Indirect Damage词条）
∴Indirect Damage是 non-combat damage.
∵Non Combat Damage is always applied as soon as it is assigned before any other actions can be taken. （FAQ1.1 Non Combat Damage词条）
∴Non Combat Damage有assign步骤和apply步骤
∴Indirect Damage有assign步骤和apply步骤
∴toughness可以在Indirect Damage的assign步骤中cancel damage
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这是我的个人理解。
