From Path of the Vampire Wiki
Dying as vampire simply refers to being sent to the Shadow Realm. In order to be sent to the shadow realm, you must be drained of all blood followed by a critical wound. You may also choose to 'kill' your character on the settings page.
While you are in the Shadow Realm you will find spirits and other vampires to drain anima from. The first few levels only require 5 anima to leave. After level 5, you will require 15 anima to leave. Once you have acquired your necessary anima, you must then find an exit to return to the living world.
There are powers that can assist. Immortals can use life link which allows them to leave after gaining their anima without the need of an actual exit. Some fadewalkers can also enter and exit the Shadow Realm at will, so long as they have not been sent there through death. This allows them to share their anima with allies to help them exit sooner.
Upon returning from the Shadow Realm you will acquire a 'Death wound' that has a random stat loss of 2 points (3 for necromancers). Death wounds last for 3 months time and appears on your wounds page. If you kill yourself, the death wound will have additional penalties in stat loss.
Death as a human is currently permanent. When you have been drained of all your blood, the last vampire to feed from you is given an option to 'kill' or 'turn' you. If you are killed you will be sent to the Shadow Realm. As a human there is no way to leave. However, in the future there are plans to allow humans the option of becoming zombies and/or ghosts, so all may not be lost for your human character if you have been killed.
If a vampire decides to turn you, they will become your sire. There is no way to reverse this unless you choose to delete your character completely. Your stats will raise to the starting stats of the path you chose at character creation plus any additional stats you earned as a human.