Promo cards can include special cards from Disney events, tournament and Set Championship promo cards, and other promotional cards for things like gift sets and more
This can absolutely destroy some players in the late game where all it takes is one slip to concede victory
Sing/Play it before challenging with your characters to get maximum value
In a metagame where graveyard recursion strategies like Amber Emerald Dogs are everywhere, this is a massive advantage because it prevents the opponent from simply bringing their threat back to life the following turn
Steel characters, such as Anna True-Hearted, keep your quests safe with high resilience, while items like Imperial Bow give a significant combat advantage, granting keywords like Challenger and Evasive to tip fights in your favor
With 2 Lore, you can even choose Fergus himself to make sure he gets at least a turn alive when Elsa The Fifth Spirit exists, and can quest without worrying about cards like Strength of a Raging Fire