The warlocks began to close ranks, falling back to make a stand under the jutting edge of the roof, where they could protect the orrery.
The warlocks were protecting something in the orrery.
mnli hypothesis: The warlocks were protecting something in the orrery. premise: The warlocks began to close ranks, falling back to make a stand under the jutting edge of the roof, where they could protect the orrery.