WTF is NPC Rivals?!

About NPC Rivals, from BoardGameGeek:

NPC Rivals is a deckbuilder. Play Hero, Loot, Monster, and Action cards from your growing deck to complete quests that require specific combinations. Each quest is added to your quest log to score big XP, but you’ll need to outplay your rivals in a constantly shifting marketplace to stay ahead. Cycle through quests to find the ones that suit your build, grab powerful cards from the market, and complete your quests before everyone else, but only one NPC will be crowned the real "main character."