Malvernis

Malvernis is a secret boss in Dragon Age II Legacy. Once the Warm Orb is obtained, it's required to go all the way back to Vimmark Wasteland to the location where you first encountered a Bronto. Once you get there you will see a Pulsing Obelisk which is only visible after acquiring the Orb. Activating the Obelisk will spawn Ghostly Archers who you need to kill as fast as you can or they will respawn. Once they are all dead Malvernis will appear.