Take the tour ×  This question regards the pathfinder setting:
I'm having a bit of confusion as to how a death by constitution
drain would take place, specifically with these rulings taken
from the Pathfinder SRD:  Each roll of a Hit Die (though a
penalty can never drop a result below 1—that is, a character
always gains at least 1 hit point each time he advances in
level). This rule suggests to me that a character will always
have at least 1hp per HD, regardless of penalties, such as
constitution drain. However, when looking under how much hp is
lost after constitution drain, you find this:  Damage to your
Constitution score causes you to take penalties on your
Fortitude saving throws. In addition, multiply your total Hit
Dice by the Ability Damage penalty and subtract that amount from
your current and total hit points. Lost hit points are restored
when the damage to your Constitution is healed.  So now, if we
take a 5th level character (5 HD) with 16 Constitution and 35hp
who took 7 points of constitution d