Rule requiring a crawler to keep killing or lose their blood bar, sometimes active during Faction Wars.
Blood bar rules are sometimes in effect during Faction Wars, meaning a crawler cannot camp in a Saferoom without leaving to kill something at least once every ten hours. Rosetta used exactly this to eliminate the saferoom system as Princess Vinata's hiding place — that, plus the fact that safe room doorways would show themselves and no naga has ever been seen using the personal saferoom system.
Princess Donut asked whether blood bars really don't drain inside the Desperado Club and Club Vanquisher. Carl confirmed it: you need a full blood bar to enter, but once you're inside it doesn't drain. Clarabelle told him that back on the Sixth Floor. That quirk is what makes a club a viable long-term hiding place when a saferoom is not.
The rule that rules out saferooms and makes Club Vanquisher a plausible hiding place.