[RPG] How much max HP should the Demilich have

dnd-5eerratahit-dicehit-pointsmonsters

The demilich statblock on Monster Manual page 48 says:

Hit Points 80 (32d4)

but outside of the statblock, the demilich's description on the next page says:

Undead Nature. A demilich doesn't require air, food, drink, or sleep. So great is the demilich's will to survive that it always has the maximum number of hit points for its Hit Dice, instead of average hit points.

Old printings of the MM said its hit points were "80 (20d4)"; this seems like it was correct assuming maximum HP, but the 2018 MM errata changed it to the current 80 (32d4).

However, if you give them the maximum number on their hit dice as of the 2018 errata, it sums up to 128 hit points. So should the Demilich actually have 128 HP listed in their statblock? Or was the change in errata an error?

How much max HP should the Demilich actually have?

Best Answer

The designers likely wanted 80 Hit Points

Because they were consistent in saying the Demilich has 80 Hit Points and they didn't contradict the Undead Nature trait in the errata it seems likely that the change to Demilich hit dice was a mistake and that they intended for the Demilich to have 80 Hit Points.

That being said the DM can freely adjust the Hit Points of a monster if they so choose. The DM is actively encouraged to modify such aspects as appropriate so in terms of rules there is no "should" when it comes to monster HP except in terms of matching CR to the players.