Nastrog is a fortified town in Verden, one of three strongholds on the border with Cintra along the north side of the Yaruga, under the control of Ervyll. The other two strongholds are Rozrog and Bodrog. The false Ciri was held here.
“
'If they have truly learned anything', Henselt shrugged, 'they will not cross the Yaruga. The river estuary on the border between Cintra and Verden is still controlled by Ervyll and his three strongholds: Nastrog, Rozrog and Bodrog. They cannot be seized just like that — no new technology is going to help them there.'
”
— pg(s). 215, Blood of Elves (UK edition)