I'm a doctor, not a mechanic
A vacuum zone kills any player that enters it. It's just another messy way to die. This class behaves in a very similar manner to the PressureZone class, except that it doesn't need to be triggered.
Hint: because the "%k" is missing in its default DamageString
%o was depressurized, the death message is not shown. See Message Placeholder for details.