In this dream Pinkie Pie was also known as Laughing Death the harlequin assassin. Blessed, or cursed depending on your opinion, by the demon Discord; the Lord of Chaos has gifted the pink one with some of his chaos magic.
Now the pink one hunts to free the world of the Lich-King Al-Connikkrall and those who willing serve his ambitions. Also she releases those who's souls have been trapped and enslaved by the lich so they can move on in the Great Cycle.