Crawlers may change floors only through their authorized stairwell; all other cross-floor portals reject their bodies.
Rosetta states that no crawler may skip floors or descend by any mechanism other than a stairwell. At the end of an earlier Faction Wars, a victory-party portal admits sponsor armies and unwilling NPCs but stops a crawler like a glass wall.
An orc reaches back through the barrier, lassoes the crawler, and pulls. The rope and equipment pass through, but the crawler body cannot, cutting the person in half.
The same rule explains why Sheol portals make equipped crawlers explode: their gear is pulled to floor fifteen while their bodies are blocked from traveling there.
A crawler stopped by an invisible portal wall while rope and equipment pass through to another floor.
The prohibition turns unauthorized portals into lethal equipment-extraction hazards instead of alternate escape routes.