This fortress isn't a building; it's an undead

As the teleportation gate activated, the five gates within the fortress began emitting black mist, and Alex's figure appeared before the siblings.

Alex started examining the fortress. Setting aside other features, the space was vast and spacious, capable of accommodating 30K small-sized undead without any issues.

With her highest level of access, Alex could gather more information than the siblings. She first went to the turrets to inspect the undead cannons.

These cannons were integrated with the turrets, immovable, and could only fire from the fixed battlements, though their angles could be adjusted.

"Strange, how do they fire without ammunition?" Alex wondered aloud. "Don't tell me I have to make the ammo myself. If that's the case, these cannons are useless."

Wait, Alex noticed a hole at the back of the cannon. Could it be that undead were supposed to crawl inside and be used as ammunition? That seemed absurd.