Advancement

The GM can improve a creature by increasing its Hit Dice. The Advancement entry indicates the increased Hit Dice (and often size) of the creature or indicates that the creature can advance by character class.

Increasing Hit Dice

As a creature gains Hit Dice, many of its game statistics change.

Size: Adding Hit Dice to a creature can also increase its size. An increase in size affects a creature's Defense, attack rolls, and grapple checks, as shown on Table: Creature Sizes, as well as physical ability scores and damage, as shown in the descriptions of the creature types.

Defense: An increase in size affects a creature's Defense, as shown on Table: Creature Sizes. An increase in size might also improve a creature's natural armor bonus to Defense, as shown on Table: Adjustments to Physical Abilities and Natural Armor. Note that a natural armor bonus stacks with an equipment bonus from armor.

Attack Bonus: Table: Creature Saves and Base Attack Bonuses shows how a creature's base attack bonus improves as it gains Hit Dice. A change in the creature's size also modifies its attack rolls, as shown on Table: Creature Sizes. Both values must be counted when recalculating a creature's attack bonus.

Grapple Modifier: An increase in size affects a creature's grapple modifier, as shown on Table: Creature Sizes.

Damage: An increase in size also increases the amount of damage a creature deals with its natural weapons.

Saving Throws: Table: Creature Saves and Base At-tack Bonuses shows how a creature's saving throw bonuses improve as it gains Hit Dice.

Ability Scores: An increase in size affects a creature's Strength, Dexterity, and Constitution, as shown on Table: Adjustments to Physical Abilities and Natural Armor.

Skills and Feats: As shown on Table: Bonus Skill Points and Feats by Creature Type, a creature may gain additional skill points and feats depending on its type.