Extended Racial HD-Class Level Swap (3.5e Variant Rule)
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 Variant: Extended 1 HD-Class Level Swap
One thing you may have discovered is that having a character with more than one racial Hit Dice makes it difficult to allocate skill points due to the number of skill points received at first level, and what skills are considered class skills for those ×4 skill points.
Unless you're a fey, dragon, or outsider type, it's very difficult make an effective skill-based character (e.g. rogue, ranger, factotum, etc...). If you try to make something like a spellcasting- or psionic-heavy gnoll, your ranks in relevant skills (Concentration, Knowledge, Spellcraft, Psicraft, etc...) will suffer more than a similar character of a 1-Hit Die race that started off as a spellcaster and took a 2-level dip into a different class(es).
The following variant is designed to help alleviate these problems.
 Variant Game Rule Information
Any character (not just those of the 1-Hit Die races) has the option to replace its first (and only its first) racial Hit Die with a class level, and receive all the first level benefits that come with it (×4 skill points and max hp for PCs and elite NPCs). Below is an example that uses a bugbear with it's first HD swapped out for a level of rogue.
|Male bugbear rogue 1|
|CE Medium humanoid (goblinoid)|
|Init/Senses||+3/darkvision 60 ft., scent; Listen +8, Spot +8|
|Languages||Common, Draconic, Giant, Goblin|
|AC|| 19, touch 13, flat-footed 16|
(+3 natural, +3 Dex, +2 armor, +1 shield)
|hp||21 (3 HD)|
|Speed||30 ft. (6 squares)|
|Melee||mwk morningstar +6 (1d8+3)|
|Ranged||javelin +4 (1d6+3)|
|Atk Options||sneak attack (+1d6)|
|Abilities||Str 17, Dex 17, Con 14, Int 14, Wis 10, Cha 6|
|Feats||Alertness, Weapon Focus (morningstar)|
|Skills||Climb +7, Craft (trapmaking) +6, Hide +9, Intimidate +2, Listen +8, Move Silently +13, Search +6, Spot +8, Use Magic Device +2, Use Rope +7|
|Possessions||masterwork light wooden shield, leather armor, masterwork morningstar, 5 javelins|
The biggest pitfall for this variant is that more often than not, the character is going to be slightly more powerful than with just the racial Hit Dice. In many cases, this increase isn't enough to warrant an increased level adjustment, and the times where it may be warranted, it only requires the level adjustment to be increased by one. The responsibility of determining which creatures warrant an LA increase falls squarely on the DM's shoulders.
To calculate the creature's challenge rating, use advanced monster challenge rating rules.