This campaign is going to be less deadly than my previous campaigns have been. That being said, death is going to carry a more significant penalty as well.
The death penalty will be 50% of the dead players current xp into level, and all other members of the party will take half of that number.
Liddia the rogue is lvl 10 and dies. She was 7000xp into lvl 10 (3000 xp away from hitting lvl 11). This means she will lose 3500xp (half of the xp she had gained after attaining her current level). All other members of the party will lose 1750xp (half the amount Liddia lost).
Note, this does not resurrect her. Resurrections are rare in this world, and her party will need to find a way to bring her back, or else the player will need to create a new character.
Also note, if the player who dies had exactly enough exp to reach their current level, they lose 1/2 the xp of the previous level.
Using Liddia as an example again, if she JUST hit level 10 (took 9k xp to go from 9 to 10) and dies, she would lose 4500xp, and the rest of the party would lose 2250.