Within the spires you described dwell the main lieutenants of the Scourge leader, the high priests. Not only do they command the Scourge forces, but they hold the key to the necropolis above, and their master.
An endless stream of Scourge minions will overrun us if we can't find and defeat their leader. I cannot leave my people defenseless, however much Durm might want to bring the fight to the enemy. It falls to you, <name>, to slay the high priests and take the scrolls they hold.
We must get into that necropolis if we're to break through the Scourge and clear a path for the villagers.
<Chieftain Wintergale reads the words written on the scrolls.>
'Shabtir bakh sokhen.'
Words of the ancient, harsh language used by the Nerubians, and apt ones at that.
'The servant bows to the master's authority.' These are the words that will gain you entry into the necropolis.
High Priest Naferset in the Spire of Decay is not targetable until you kill all three En'kilah Necromancers in the room, and High Priest Talet-Kha is not targetable until you destroy the mystical webbing that suspends him.