We succeeded in taking the Sanctum. We can continue to convert sentries and use them as guards at other tactical locations.
I’ve crafted new crystals that will bring more of them under our control; place them inside the hulls of defeated sentries. We’ll deploy them to other locations once they’re converted.
Vindicator Xayann at the Shattered Sun Staging Area wants you to place the Attuned Crystal Cores inside 5 defeated Arcane Sentries to turn them into friendly units.