Monster PCs

Introduction
3rd edition D&D has made playing a character of a non-standard race a viable option. Granted, it still requires DM approval, but by providing a system to incorporate even powerful monsters into a party while keeping their level of power close to that of the usual humans, elves and dwarves makes it easier for DMs to consider allowing characters of unusual races. In theory.
Judging from recurring questions on the message boards dedicated to the game, it seems the rules are far from clear, not to mention the fact that only a minor fraction of monster races has been given an ECL rating. Thats why I'll try and provide a clear and consistent dicussion of the process of turning your average monster into a full-fledged hero.
Most of this description will adhere to the rules set out in the DMG and/or the FRCS, but at certain points I'll use rule interpretations that smooth things over. Dont be alarmed by this. It will make the rules make sense, and therefore easier to remember and apply. References are provided to distinguish official rules from rules interpretations. Also provided are a link to several variant rules, as well as a link to an ECL calculator.

Monster Races
Anyone who has tried his hand at creating monster PCs will be aware that D&D distinguishes between two categories of monster races: races with one or fewer HD (Orc, Human) and races with more than one HD (Bugbear, Gnoll). Templates may seem a separate category at first glance, but for this discussion only the number of monster levels matters. Some templates add or replace HD (like Montes Ghoul template), and might thus change the category a race belongs to. Come to think of it, Dragons, with their age categories, might be considered a category of its own, but I'll save that for the variant rules page.

Lets start with the basic rules that apply to both categories (in the order in which they appear in the MM stat blocks):
· Size and type are determined by race.(MM, p. 5)
· The HD of the first level, be it class or monster level, is always treated as maximum. This is because PCs are elite characters. (DMG, p. 24)
· Initiative is independent of race. (MM, p. 6)
· Speed is determined by race, though class, armor and encumbrance affect it as usual. Note that Swim and Climb speeds include a +8 racial bonus to the appropriate skill.
· The natural armor class bonus is determined by race (the +0 natural armor bonus of many races isnt mentioned in the stat block). (MM, p. 6)
· BAB works differently for each type and is discussed below. Races with natural weapons can choose to use these instead of weapons. Natural weapons use the attack routine given in the MM. The number of natural attacks per round is based solely on race, independent of BAB, unless the race has a single slam attack (then it works as if using a weapon). (MM, p. 7 & WotC MM board FAQ) Monster PCs can use the monster attack routine as given in the MM or combine it with weapons. In the latter case all natural attacks not replaced with a weapon become secondary attacks (the Multi-attack feat applies) and the weapon uses iterative attacks based on bab as usual. (WotC MM board FAQ)
· Face and reach characteristics are determined by race. (MM, p. 7)
· Special attacks are determined by race. Note that the DC of these attacks often equals 10 + half the creatures level + the creatures Cha modifier (use total number of HD for level in this case). Also note that special attacks based on items (for example a sprites sleep arrows or a satyrs pipes) are not automatically granted by chosing that particular race. It is strongly suggested to limit psionic creatures at will powers (including psionic attack, but not defense modes) to three uses per day per power. (MM, p. 8; unofficial PsiHB errata)
· Special qualities are determined by race. The type of vision (normal, low-light or darkvision) is often determined by type. (MM, p. 8 & 5)
· Racial ability adjustments are based on the scores given in the Abilities entry in the MM stat blocks. For scores of 10 or higher, the adjustment is determined by substracting 10 from even scores and 11 from odd ones. For scores below 10 no real adjustment is determined. Instead a set of two tables (one for Int, one for the other ability scores) is used: tables 2-5 and 2-6 on page 23 in the DMG. All PCs use 4d6, drop lowest (or another, equally advantageous method) to determine base ability scores. (DMG, p. 23)
· PCs of any race advance by class or by HD, player's choice. (DMG, p. 23)

Advancement by HD instead of by class
Many monsters in the MM have an advancement range expressed in number of HD. Use MM page 13 to determine the effects of adding a monster level. Use the original size of the creature to determine the number of EHD.
Often the size of such a monster increases after gaining a number of monster levels, which greatly enhances its combat ability. This may seem unbalancing, but considering that monster levels tend to be worth decidedly less than real class levels, it wont be as bad as you might think at first glance. There is something to playing the biggest Barbazu this side of the river Styx, that is more tempting than playing a Barbazu with fighter levels tacked on. Advancing by HD works just like multiclassing with another class would. (MM, p. 12)

The Climate/Terrain and Organization entries can be used as guidelines for background creation. The CR and treasure entries are meaningless for PCs. The alignment entry just gives the alignment a member of that race is most likely to have, and should not be treated as a straightjacket for a PCs alignment (see MM page 12 for more details).

That leaves us with the following entries for discussion: HD, BAB, Saves, Skills and Feats. Since these depend on the type of race (and number of HD), lets look at both types separately.

Races with one or fewer HD
When creating a PC of this category, replace the single HD with the HD of the chosen class.
These races, like the standard races, use class to determine HD, BAB, saves, skills and feats. The skill points at 1st level, the number of which is determined by class, are quadrupled as usual. The Skills entry should be ignored as it has no effect, not even on which skills are class skills and which are not. (DMG, p. 24) Racial skill bonuses, if any, are mentioned separately in the text below the stat block. (MM, p. 11)
Note that the number of feats gained is only 1, regardless of the number of feats in the Feats entry.
The feats given in the MM, represents the choice an average member of that race would make, and can be replaced with any other feats of the players choice (limited by the feat's prerequisites). Monster PCs may choose feats from among those given on MM page 11, provided they meet the feat's prerequisites. (Dragon's "How to Create a Monster: Recipes for Disaster" article, but can also be inferred from MM monster entries)
Psionic creatures may choose psionic feats, and are considered to have enough power reserve for feats that require this to work. (inferred from PsiHB monster entries)
Weapon and armor proficiencies are determined by class (alone). (DMG, p. 22)

Races with more than one HD
When creating a PC of this category, you determine HD, BAB, saves, skills and feats using the creatures type (Humanoid, Giant, Shapechanger, etc.). I'll address adding class levels later.
The number and type of HD (or monster levels) is given in the HD entry. Remember that the first HD is maximized, and the others are rolled to determine HP (Con modifiers apply as usual). The number of HD determines BAB and base saves, using the table on MM page 13. (MM, p.5-13)
Determining the number of skill points works very differently from what you're used to. Monster PCs get skill points based on their type. For most types (not Dragons and Outsiders) this means they get a number of initial skill points plus a number of bonus skill points based on the number of HD they have (as set out in the tables below).

Initial Skill Points
None: Construct, Ooze, Plant.
10-12: Vermin.
10-15: Animal, Beast.
6 + Int modifier: Giant, Humanoid.
2 x Int score: Aberration, Elemental, Magical Beast, Monstrous Humanoid, Shapechanger.
3 x Int score: Fey, Undead.

This is taken from the table on MM page 11 (based on type) and modified for errata.
For those with a range of skill points (like Animal), I suggest you take the upper limit, as PCs are elite characters.
In addition to these initial skill points, monster races of many types, get extra skill points based on the number of HD they have, the so called Extra HD (EHD). Extra HD are HD in excess of the number normally associated with a creature of a certain size. For medium or smaller creatures this is 1, so subtract 1 from the number of HD given in the HD entry to determine the number of EHD for a medium or smaller creature (ignore negative numbers, these count as zero EHD). The same goes for larger creatures, except that the number of HD you substract increases with size (2 for Large, 4 for Huge, 16 for Gargantuan, 32 for Colossal). For elementals the number of base HD is somewhat different (Medium 2, Large 4, Huge 8, Gargantuan 16, Collossal 32). (MM, p. 11 and MM errata)
Note that there is no quadrupling of skill points for PCs of this category. (MM, p. 11)

Bonus Skill Points
None: Animal, Construct, Ooze, Plant, Vermin.
+1/EHD: Beast, Giant, Humanoid, Magical Beast, Shapechanger.
+2/EHD: Aberration, Elemental, Fey, Undead.
Skill points for Dragons and Outsiders work differently. Creatures of this type get skill points per HD, much like a class (but even these do not get x4 skill points for their first HD, nor do they retain these skill points if they have but 1 HD).

Dragon and Outsider Skill points per HD
6 + Int modifier per HD: Dragon.
8 + Int modifier per HD: Outsider.

The skills mentioned in the Skills entry, unlike the one or less HD category, determine which skills are considered class skills for the creatures monster levels. All other non-exclusive skills are considered cross-class skills. Racial skill bonuses, if any, are mentioned separately in the text below the stat block. (MM, p. 11)

The number of feats a monster PC gets is determined by its type and the number of EHD the race has (as set out in the tables below).

Initial Feats
None: Animal, Beast, Construct, Ooze, Plant, Vermin.
1: Dragon, Giant, Humanoid, Outsider.
Int modifier (min 1): Aberration, Elemental.
1 + Int modifier (min 1): Fey, Magical Beast, Monstrous Humanoid, Shapechanger, Undead.

For balance reasons, use the Int modifier of an average specimen of the race (as specified in the monster manual stat block, which is often the same as the racial Int adjustment) not the Int modifier of the individual in question. Thus, because an average centaur (monstrous humanoid - initial feats 1 + Int modifier) has an Int modifier of -1 (Int 8), this results in one initial feat for any centaur (1 - 1 = 0, minimum 1), regardless of the individual centaur's Intelligence score. Because the article is designed for building new monsters, not for monster PCs this issue is not covered, but it seems the most logical and balanced option. Otherwise there would/should be a note in the Monster Manual that an unusually intelligent centaur (with 12-13 Int score) would gain one additional feat, and an extremely intelligent centaur (with 14 Int) would gain two additional feats. There is no such note in the Monster Manual for centaurs or any of the other races that would likewise be effected. So using the average creature's Int modifier seems in order.

In addition to these initial feats, monster races of many types, get extra feats based on the number of HD they have, the socalled Extra HD (EHD).

Bonus Feats
None: Animal, Beast, Construct, Ooze, Plant, Vermin.
+1/4 EHD: Aberration, Elemental, Fey, Giant, Humanoid, Magical Beast, Monstrous Humanoid, Shapechanger, Undead.
+1 per 4 HD*: Dragon, Outsider.
* Dragon and Outsider races get a bonus feat per 4 HD, regardless of size.

Please note that the above method of determining number of feats is included for completeness' sake only. You might as well just count the feats given in the Feat entry of the monster writeup. Do keep an eye out for racial bonus feats, which cannot be replaced by other feats.

Again the feats mentioned in the MM monster entry are examples and can be replaced with feats of the players choice. Monster PCs may choose feats from among those given on MM page 11, provided they meet the feat's prerequisites. (Dragon's "How to Create a Monster: Recipes for Disaster" article, but can also be inferred from MM monster entries)
Psionic creatures may choose psionic feats, and are considered to have enough power reserve for feats that require this to work. (inferred from PsiHB monster entries)
Giants, Humanoids, Monstrous Humanoids and Outsiders are proficient with all simple weapons and any weapons mentioned in entries. Outsiders with an Int score of 6 or higher are proficient with all martial weapons. Note that each creature is proficient in whatever type of armor (light, medium or heavy) that it is described as wearing, as well as all lighter types. Creatures not listed as wearing armor are not proficient with armor. (MM p. 5-7, MM errata)

Adding class levels to races with more than one HD
Adding class levels works exactly the same as multiclassing (considering the monster levels an additional prefered class). (DMG, p. 24) So for the 1st class level, the HD isnt maximized, nor are the skill points quadrupled, just like they wouldnt be if a human fighter added a level of rogue. Note that this also means that for purposes of buying skill ranks, only skills that are class skills for the added class level can be increased one-for-one, while all other non-exclusive skills even those that are class skills for the monster levels- cost two-for-one. The gaining of new feats and stat increases is based on character level, so the time has come to talk about ECL.

Equivalent Character Level (ECL)
There are a lot of misconceptions about this admittedly vague term. First off, it is not at all the same as EL (encounter level). It also has no mathematical relationship with CR whatsoever. It has very little to do with number of HD, either. That number forms the lower limit for the ECL modifier, but thats it. Determining the ECL of a given race is a matter of guesswork. A framework for this guessing game is provided on the ECL Calculator page (see above).
Now you know ECL is hard to determine, but fortunately some values are provided in the DMG (page 22), the FRCS or OA.

Dragon #293 provides a list with ECLs for creatures in the MM, but I suggest you do not use these, as these are incompatible with the DMG examples (too high overall, and there is no pattern in their changes from the old values). The same goes for some of the FRCS errata (except the Kir-Lanan, which was obviously a mistake at +2).

So now that you have this ECL, what do you use it for?
ECL, or better, the ECL modifier, is used to determine a PCs character level for determining starting gold (despite what the DMG says), starting xp, xp needed to reach the next level and average party level. You do this by adding the ECL to the number of class levels a PC has. (FRCS, p. 21) Now there are a lot of other purposes for which you need to know a PCs character level, like gaining new feats, increasing ability increases and determining the number of uses per day for certain feats. For all these you should use the total number of HD as character level instead. (MM, p. 14)

Gaining new feats and ability increases
For races with one or less HD this works exactly the same as for the standard races. For races with more than one HD this is not the case. For such PCs you use total number of HD to determine whether or not a PC should get a NEW feat or ability increase (do not use the HD equals character level retroactively). (MM, p. 14) The number of feats gained from monster levels is already determined, as are ability increases (subsumed in the racial adjustments). If, after adding a class level to such a monster PC, the total number of HD is divisible by 3, the PC gains a new feat. The same goes for ability increases, when the number of HD is divisible by 4.
A 14 HD Stone Giant PC gets 4 feats (a giant starts with 1 feat and gains 1 per 4 EHD, he has 12 EHD), not 5. After gaining 1 class level, he has 15 HD, which is divisible by 3, so he gains a new feat. Adding another level brings him to 16 HD, divisible by 4, so he gets an ability increase.

Epic Monster PCs
To determine whether or not a Monster PC is an epic character (and thus allowed to take epic feats), one need only look at its equivalent character level (ECL modifier plus class levels). As soon as this level exceeds 20, that character is to be considered an epic hero. (ELH, p. 155)

Spell-like abilities and races casting as specific classes
These special abilities of a monster deserve special attention. Both are affected by adding class levels of the appropriate classes. Spell-like abilities increase in power when you add levels of the appropriate class. For example, a Lamia can use Charm Person once per day, as if cast by a 9th-level sorcerer. Should that Lamia add a sorcerer level, her Charm Person will work as if cast by a 10th-level sorcerer (9+1). Adding a wizard level won't have any effect, as the spell-like ability is cast as a sorcerer, not a wizard. This increased level affects spell stats like duration, range and (possibly) damage, as well as how hard it is to dispel the effect, or the caster level used to by-pass SR.
There are exceptions, like the planetouched, where every level added increases the power of such abilities, regardless of class. These races include a desrciption like: "as cast by a sorcerer of 1st level or their character level, whichever is higher". Use total number of HD for character level in these cases.
Next, there are races that have casting ability as a xth level spellcaster. Adding a level of that spellcaster class stacks with these 'fake' levels with regards to spells per day and caster level (not for things like HD and Wildshape). A good example of both types of special abilities is the Nymph, with Dimension Door (7th level Sorcerer) and the casting ability of a 7th level Druid. Adding a Sorcerer level to the Nymph will increase her casting level of Dimension Door to 8th (increasing range and resistance to dispelling magic), as well as giving her all the abilities of a 1st level Sorcerer. Adding a Druid level, however, will give her all the abilities of a 1st level Druid (HD, Nature Sense, etc.) but the casting ability of an 8th level Druid (including acces to 2 4th level spell slots) instead of that of a 1st level Druid. (MM FAQ and examples on the Wizard's site)

The DC of supernatural abilities
There are several abilities tied to the amount of HD a creature has, like SR, Poison, various supernatural abilities like energy drain etc. For all of these you should use total number of HD (monster and class HD) to set the DC, if the DC is dependent on number of HD or level. I know there are people who claim only monster HD would increase the power of these abilities, but I say that the usefulness of these abilities will lessen at higher levels even when using total number of HD and enough so that using the less advantageous monster HD only will make them pointless. Remember that you pay for them with ECL, and that is a hefty price. (couldn't find a strong reference pointing one way or the other, though the vampire (MM, p.221-222) would suggest that class HD count towards HD. DC of 10 + 1/2 vampire's HD + vampire's Cha modifier. DC 13 for 5th level fighter example, +1 from Cha, +2 from 5 HD)