Creature Templates

Reading the SRD, one might think there are only two types of creature templates (changes that can be applied to a creature to make it more powerful).  These are: acquired and inherited templates.

Acquired templates are supposed to be templates that are added to a creature well after it has acted as a a non-templated version of the creature, and includes such things as lycanthropes (were-wolves, were-rats, etc), ghosts, zombies, skeletons, liches and vampires.

Inherited templates are supposed to be templates that are part of the creature make-up from the beginning, such as fiendish, celestial, half-fiend, half-celestial and half-dragon (but which may also include lycanthropes!)

When attempting to program these, I can identify four semi-distinct categories:

Altered Species

Fiendish, half-fiend, celestial, half-celestial and half-dragon fall into this category.  Typically used for creatures that do not progress by character class (or have some progression with “racial power dice”).  Rather than use the standard species traits and progressions, the altered progressions and traits are used instead.

Replacement Creature

Ghost, skeleton and zombie fall into this category.  There is a base creature instance which is used to build out the replacement creature.  The original creature needs to be tracked in case the template is removed (that is, the condition that made the replacement creature is undone).

Replacement Creature with Advancement Alterations

Liches and vampires use this style.  The base creature instance is used to build a replacement creature, but the creature can advance in character class.  Any subsequent character class advancement may be altered from its normal class features (typically power dice size), but also may include strengths of special powers such as spell resistance.

Advancement Class Analog

Lycanthropes gain a number of “racial power dice” indicated by the type of lycanthropy.  These act like a character class, but care needs to be taken in removing the “affliction” (class and power dice) since it is possible to advance in character class level after gaining the “affliction”.