When your astral form is killed by an astral being within a Domain you die. The only way to avoid death is to use a Domain Bounce, Domain Bounces happen shortly after death and revive your astral form. Everyone naturally has three bounces but by defeating large numbers of astral beings and in some cases small groups of UESs you can obtain even more Domain Bounces. As long as you don't run out of Domain Bounces you won't die in a Domain. Make sure you keep count of how many Domain Bounces you have, loose track and you could loose your life.