On Monster Creation

While the standard character-building system can be used to make most challenges, not everyone wants a campaign filled only with mostly humanoid sapient creatures as their only combat obstacles. Below the details on how monsters, dragons, animals, constructs and so, are created.

All creatures are created with these base stats: 18, 16, 16, 14, 14, and 12 distributed to where it is best for the creature. These can be upgraded more to match how players grow. Instead of magical items though most creatures should have their base stats modified to match or exceed the average player's stats at that point.

Terms

Bonded Armor: Bonded armor is armor that simulates the stats of the kind of armor a character would wear, but is fused with the creature. This is most common in constructs, elementals, and attendants. Bonded armor cannot be looted, as it is either fused to, part of, or otherwise bonded to the creature.

Natural Attack: Natural attacks are things like claws, fangs, wings, tails, etc. Typically a monster has a primary, often claws or a bite, that has the highest bonus. All other natural attacks are at a -5 bonus during a full round attack. On any full-round attack, a monster uses ALL of its natural attacks. If they cannot full-attack they will typically opt for their primary natural weapon. Weapon focus (Unarmed), and its counterpart feats, apply to all natural weapons.

Definitions

Much like making a character, the first thing we need to do is pick a primary creature definition for the monster. These are not to be taken by players without a great deal of consideration by the DM first as most of these are intended to make challenging foes for equivalent level characters. Creatures can also have a series of secondary definitions. Primary definitions sometimes modify the Hit Dice type of a creature or limit the types of magical progressions it can have.

Primary Creature Definitions

Aberration

Weird, impossible, or eldricht creatures are considered aberrations. A creature made up of eyed tentacles, for example.
Armor: Natural or Bonded
Limitations: None
HD Modifier: d8 always
Effect: Aberrations always have at least 2 extra abilities unique to them, they will always be fear or compulsion based. All aberrations gain +2 Constitution, +2 Wisdom, and +4 Charisma to their base.

Animal

Animals are natural creatures that live in the prime plane of the world. They are typically non-magical
Armor: Natural or barding
Limitations: Int has to be 3 or lower, cannot take any magical progressions or abilities, are restricted to the use of natural weapons only, and have reduced skill options: see effect. An exception to the non-magical abilities would be if they have an elemental secondary definition. In this case they can take related matching elemental abilities.
HD Modifier: d8 always
Effect: Animals can only selected the following skills: acrobatics, balance, bushcraft, escape artist, intimidate, move silently, Discern Intent, and swim. They gain skill points as if their intelligence is 10. The skills Spot and Listen always have maximum skill points in them.

Attendant

Lesser angels, lesser demons, and nature spirits are attendants. Any creature that is born and created to serve a concept or god would have this definition.
Armor: Any
Limitations: Uses Player type progressions
HD Modifier: Based on progression
Effect: Attendants always have a smiting ability of sorts. They fall prey to the banish spell and similar effects. All attendants gain, +2 Dexterity, +2 Intelligence, and +2 Charisma.

Construct

An artificial creature of any kind. These are capable of anything so long as it was built to do whatever it does. Constructs cannot grow on their own and must be modified or updated by an intelligent creature.
Armor: Bonded
Limitations: Cannot gain skill points, they must be built in a way to grant them bonuses to said skills. They have no intelligence or constitution scores.
HD Modifier: d12
Effect: Intelligence and Constitution are n/a. Constructs are immune to all critical hits, opportunist strikes, compulsions, glamour, and health related effects. Constructs above medium size gain +2 hp per hit dice per size category larger. For example a 4 HD huge construct would gain a +16 to its HP.

Dragon

Highly intelligent quadrupedal winged lizards that command aspects of nature. There are other things in the dragon family as well such as drakes, wyverns, and so on.
Armor: Any
Limitations: None
HD Modifier: d12
Effect: Dragons gain all dragon definitions from the player lists. They also gain access to the monster dragon secondary definitions.

Elemental

Denizens of the elemental planes, these creatures can be intelligent or animalistic.They always carry some kind of elemental flare
Armor: Bonded
Limitations: If an elemental is animalistic they cannot have an intelligence over 3.
HD Modifier: Based on progression
Effect: Immediately gain a secondary definition that gives them an energy type. Elementals are all vulnerable to banishing spells and similar effects.

Mythical

Gorgons, ogres and trolls, oh my! Most creatures that stories can be written about that don't fit into the other categories fit here.
Armor: Any
Limitations: None
HD Modifier: d10
Effect: Mythical creatures gain +2 Str, +2 Con, +2 Cha. Mythical creatures always have supernatural abilities. Mythical creatures often have resistances and vulnerabilities.

Plant

Fungal and plant creatures that thrive in the sun and wither when dry.
Armor: None
Limitations: Cannot gain skill points and they have no intelligence scores.
HD Modifier: d8
Effect: All plant creatures gain regeneration in the sun of at least 1 hp on its turn. Plants are vulnerable to desiccation and resistance to any light based damage. Plants do not need to eat, so long as they receive sunlight. As a result of having no intelligence score they are immune to compulsions.

Undead

Zombies, skeletons, vampires, and other cliches involving mobile non-living things.
Armor: Any
Limitations: No constitution score
HD Modifier: d12
Effect: Undead are immune to any kind of constitution save for vital or health effects. Undead are vulnerable to fire and immune to cold. Undead are immune to critical hits, sneak attacks, and injuries.

Secondary Creature Definitions

Saline

A creature from dry arid climates that has become elementally aligned with salt.
Prerequisite: None
Effect: Immunity to desiccation damage, vulnerability to cold, all natural attacks gain at least +1d6 desiccation damage.