The card can be acquired by completing the main story of The Fall of the Dark Brotherhood.
Using this card early is paramount. Destroying 20 creatures is very difficult, and takes time. One upside is that every turn, you may summon an enemy target that is +0/+1, which can easily be dealt with. Enemy cards are counted for every card that is destroyed, including ones that attack friendly creatures and die. When the 20th creature is killed, the opponent loses 20 health, you gain 20 health, and are rewarded up to 10 cards. The max cards that anyone can have in their hand at one time is 10.
Upon dealing 20 damage with this support, the player is awarded the title "The Lucky Lady."