Archives of Nethys

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Custom Species Builder


Source Interstellar Species pg. 42
When you’re creating a new species, the game mechanics might be at the forefront of your mind, yet many of the most compelling species have mechanics deeply intertwined with their physiology and culture, evoking rich visuals and narratives. If you have specific mechanics you want to use, it’s okay to start there! Don’t be afraid to look at other sections first, such as physiology or home world, and let the decisions you make there inform those mechanics.

Ability Score Adjustments

Source Interstellar Species pg. 42
Most playable species have one of two adjustments. First, they might grant a +2 bonus to a single ability score of the character’s choice (like humans). Second, they might grant a +2 bonus to two specific ability scores and a –2 penalty to a third (like vesk). The first option is simplest and recommended.

Hit Points

Source Interstellar Species pg. 42
Typically, a species grants 4 Hit Points at 1st level. In some cases, you might instead have the species grant 2 (for smaller or frailer creatures) or 6 Hit Points (for especially tough species).

Size, Speed, and Senses

Source Interstellar Species pg. 42
Most creatures are Medium size, though your species can also be Small or Large. Making a species smaller than Small requires further considerations about how they might interact with a galaxy built for larger creatures, and mechanically Tiny characters usually have 0-foot reach that makes combat difficult. On the other hand, Huge and larger playable species become difficult to incorporate with most parties and adventures; many areas just aren’t big enough to accommodate them! If you create a Large species, their default reach is 5 feet (like that of most Medium creatures), but you might give them a 10-foot reach.
The default land speed is 30 feet. A species can have a single additional movement speed, but consider the physiological source of that speed and the environmental pressures that would’ve shaped its evolution. Choose from the following list: burrow 20 feet, climb 20 feet, fly 20 feet (average or clumsy maneuverability), or swim 30 feet. You might also reduce the species’ land speed by 10 feet to increase the additional movement speed by 10 feet.
Default vision is explained on page 260 of the Core Rulebook. A species can also have low-light vision as well as either blindsense (emotion, life, scent, sound, thought, or vibration) with a range of 30 feet or darkvision with a range of 60 feet. Again, consider its physiological source and evolutionary reason for existing. You can instead give your species both the sightless universal creature rule and blindsight (emotion, life, scent, sound, thought, or vibration) with a range of 60 feet.
Finally, consider how many abilities above you granted your species. If your species has powerful extra senses, an additional movement type, and other perks so far, it might be best to pick one less regular combat or noncombat ability to keep the power level roughly in line with other playable species.

Creature Type

Source Interstellar Species pg. 43
Choosing a creature type is largely thematic, rather than mechanical. Many creature types include additional abilities like darkvision, specific immunities, or other abilities appropriate for NPCs designed using Alien Archive, yet you shouldn’t apply these abilities to your species automatically. Instead, consider them as inspiration. The creature type might inform your species’ abilities, physiology, and culture, or you might choose a creature type that best fits traits you’ve already chosen. You can also roll on Table 2-5: Creature Type on page 46 if you want to select randomly.
If your creature is aquatic, you can give it the water breathing universal creature rule. If you do, you can also give it the amphibious universal creature rule.

Special Abilities and Weaknesses

Source Interstellar Species pg. 43
Your species should gain several special abilities, which are broadly divided into combat and noncombat abilities. Your species should receive some of each to remain balanced in play against other species. Both categories have stronger abilities (the first 8 options listed on the corresponding table) and numerous regular abilities. Choose either one stronger combat ability or two regular ones, then do the same for noncombat abilities. Don’t choose the same ability more than once. As with all steps, consider the physiological or cultural sources of the ability and feel free to adjust the flavor of it to match your species concept.
You can also determine your abilities randomly. If you want to roll on a table for one stronger ability, roll a d8. If you want to roll for two abilities, reroll any results of 8 or less, as well as any duplicate results.
Weaknesses are optional, and they don’t grant additional abilities. Example weaknesses appear in Table 2–6: Weaknesses, and you can invent your own, though you should avoid sweeping penalties to AC or d20 rolls. Some weaknesses allow a saving throw (DC equals 13 + 1/2 the level, item level, or CR of the source that triggered the weakness ) to negate their effect.

Species Versus Individual

Source Interstellar Species pg. 43
It’s important to keep in mind that you’re creating a species, not an individual character (though, of course, the hope is that you and others will create characters of your new species). As such, paint in broad strokes; among individual members of a culture, there will be plenty of exceptions to the overarching trends. Also keep in mind that individual members of the species whose life experience is of an entirely different culture (or cultures) won’t necessarily have strong links to that of their species’ home world.
The most interesting part comes when creating a character of your species; you can decide how exposed they were to their home world’s culture and what pieces they strongly identify with and which they might resist.

Other Abilities

Source Interstellar Species pg. 43
It’s often appropriate for a species to have a very specific ability tied to its culture or physiology. While such abilities are beyond the scope of this species builder, which is meant to provide an easy and balanced way to create new species, you can work with your GM to create them, using the abilities presented here as rough guidelines for what’s appropriate.