Vorago is a high level boss in RS3 that drops 2 very sought after weapons. The weapons are Seismic wand and Seismic singularity. There's also a challenge to get all of the cosmetic boss gear from Vorago, called the set of Omens, you can only get 1 piece of this set a week, and the entire set must be finished before you can have a chance at getting the pet drop from Vorago, called Vitalis.
That being said, it's not worth anywhere near 2b, at least imo. Maybe to someone who does vorago 24/7 and has made several bil off of it, but the boss was released last year, so it's not like it's even an old boss.