Unless I'm mistaken it seems the Demilich has the wrong displayed average HP. It says "80 (20d4)" so either the average is wrong or the dice count/type is wrong. As it stands today I believe the hit points should be "50 (20d4)" or "80 (32d4)" or something else, but not "80 (20d4)".
The description in the MM has a note saying something to the effect of a demilich has such a strong will to live that it has maximum hit points for its hit dice. Max of 20d4 is 80.
Edit: Found it.
Undead Nature. A demilich doesn’t require air, food, drink, or sleep. So great is a demilich’s will to survive that it always has the maximum number of hit points for its Hit Dice, instead of average hit points.
Unless I'm mistaken it seems the Demilich has the wrong displayed average HP. It says "80 (20d4)" so either the average is wrong or the dice count/type is wrong. As it stands today I believe the hit points should be "50 (20d4)" or "80 (32d4)" or something else, but not "80 (20d4)".
The description in the MM has a note saying something to the effect of a demilich has such a strong will to live that it has maximum hit points for its hit dice. Max of 20d4 is 80.
Edit: Found it.
Undead Nature. A demilich doesn’t require air, food, drink, or sleep. So great is a demilich’s will to survive that it always has the maximum number of hit points for its Hit Dice, instead of average hit points.
Ahh, then it was my mistake, did not read it well enough. Thanks for pointing it out.