Use the Necromantic Detector Mk II to find the source of the scourge (right-click it and select Use). Be sure to use the Othmir Scouting Potion, as the mobs see through anything else. (it has a 6:36 minute timer).
Enter the Cave of Anguish at 4123, -1081, 2223 . You can fly in, but you're grounded inside.
The undead othmir here can see through stealth, use the potion!
Follow the cave to 3911, -1154, 2264 for the update.
Create a new batch of Hope on the Dragon Skull (which is a forge) at 3911, -1154, 2235 using the Cleansing Corruption recipe. You must take the recipe to a full four bars of progress for the update!! When you create a new batch you'll get the update.