(edited by Kesvalk.1674)
New Kryta Blueprint
I’m guessing the White Mantle was trying to build a castle in (or near) the Silverwastes to either declare secession from Kryta or declare themselves the new capital (after using asuran technology to explode Divinity’s Reach).
I draw the conclusion that the fortresses in the Silverwastes where built by the White Mantle, which still exists, and that they consider themselves part of New Kryta(which they rule) and not part of Kryta, a completely separate country. Which would help explain why Anise has sent Canach to ‘keep watch’ on the Pact, his real purpose is to root out the White Mantle…enemy of Kryta, the Royal family and the Shining Blade.
P.S. – This was a major plot point of GW1.