Os Arcanos Desenterrados Juramento de Redenção tem as seguintes características:
Aura do Guardião
Starting at 7th level, you can shield your allies from harm at the cost of your own health. When a creature within 10 feet of you takes damage, you can use your reaction to magically take that damage, instead of that creature taking it. This feature doesn't transfer any other effects that might accompany the damage, and this damage can't be reduced in any way.
At 18th level, the range of this aura increases to 30 feet.
Emissário da Redenção
At 20th level, you become an avatar of peace, which gives you the following benefits.
• You have resistance to all damage dealt by other creatures (their attacks, spells, and other effects).
• Whenever a creature damages you, it takes radiant damage equal to half the amount it dealt to you.
If you attack a creature, cast a spell on it, or deal damage to it by any means but this feature, neither benefit works against that creature until you finish a long rest.
Agora, obviamente, o dano não pôde ser reduzido pelo Emissary, mas não consigo descobrir se deve refletir metade dele.
Por um lado, você está sofrendo dano causado por outra criatura, mas por outro lado a criatura não está atacando você, você está simplesmente sofrendo dano por outra pessoa.