If this card destroys a monster by battle and sends it to the GY: You can add 1 "Magician", Performapal, or "Odd-Eyes" Monster from your Deck to your hand
Hot Red Dragon Archfiend King Calamity effect is a When Optional Effect, meaning that it could miss the timing if Crimson Dragon effect is not activated on Chain 1
If a creature enchanted with an Aura that has umbra armor would be destroyed by multiple state-based actions at the same time (most likely because a creature with deathtouch has dealt damage to that creature greater than or equal to its toughness), umbra armor's effect will replace all of them and save the creature
As a direct point of comparison, this exact Marnie card appears in English's Sword & Shield Base Set, but only commands a fraction of her Japanese value, settling at around $30
They were designed so that the small set could be drafted with each large set, with the large sets never being drafted together