How to set the hit dice of a mob?

[Dalvyn]

In the hit dice description of a unique mob (d8+2), there are two parts: the dice size (8) and the bonus (2). This information is used, in combination with the level of the mob, to determine how many hit points it will have: in this case, if the mob is level 40, it will have 40d8+80 hit points, that is between 120 and 400 hit points.

The bonus can vary between mobs. It generally ranges from +0 up to +3 for "normal" mobs (mobs with a class or usual monsters) but can go higher for very tough and/or unique monsters.

The hit dice size on the other hand, depends one on of two things: either the class of the mob (for a mob with a class, that is, a priest or rogue or ranger or ...) or the race of the mob.

The base hit dice size for mobs with a class are given below.

• Barbarians: d12
  Fighters, rangers, paladins: d10
  Clerics: d8
  Rogues: d6
  Wizards, sorcerers: d4

For other monsters, this is based on their monster category.

• Dragons (all types): d12
  Undead: d12
  Constructs (golems, mechanical constructs): d10
  Beasts (owlbears, basilisks, stirges, lamias, ...): d10
  Oozes (slimes, jellies, ...): d10
  Fey creatures (dryads, nymphs, ...): d6
  All the other creatures: d8

The other creatures (who use d8) are the following ones:

• Aberration (creatures with strange, alien body forms: beholders, cloakers)
  Animal (creatures that also exist in the real world)
  Elemental (fire, blood, water, ...)
  Giant (all kinds of giant humanoid creatures)
  Humanoid (elves, humans, ... but those generally have a class)
  Monstrous Humanoid (medusa, centaur, ...)
  Outsiders (demons, devils, ...)
  Plant creatures (shambling mounds, assassin vines, ...)
  Shapechanger (dopperganger, lycanthropes, ...)
  Vermin (spiders, beetles, ...)

[Andreas]

I'm setting the hit dice and bonus in OLC and when I save the mob, purge and reload it, the hps and level sometimes change. Can't figure out why it's doing this.

[Dalvyn]

Try using 'showrace (race_name)' for the race you use. You will see that, for each race, there is a minimum level and a maximum level. I think that simple mobs are forced to have their level between those two limits. So, if you set the level outside those limits and the mob is simple (that is, you haven't set one of its stats or another field that force the mob to be unique), the code might change the level. It might be what you experienced.