Here is an old article that I never published for Koru. It focuses on an optional humanoid race evolved from Trilobites (which are the most numerous wild animal on Island World.
Even though it’s a bit rough, and likely will change a lot when the final book goes it, it’s worth checking out!
The Trilobite folk are bipedal humanoids who share an ancestry with the most common arthropods on Koru. While there are three varieties, each with some major distinctions, they all a set of hard, segmented plates going down from the top of their heads down their backs and along their short tails. While they have lost most of their ancestors’ many limbs they have kept the ability to roll up into a hard, armored ball for defence and mobility.
There are three “types” of Trilobite-folk. All three are Amphibious, have Natural Armor (of varying degrees) and can roll up into an Armor Ball.
1. Deep: these are the ones who most resemble their ancestors: they are shorter than other humanoids (roughly 3 to 4 feet tall) and have four sets of limbs. They can assume a bipedal stance by standing on two sets of “legs”. Their insect-like hands are completely unable to use tools or weapons designed for human hands, but their hard chitinous armor allows them to naturally replicate just about any basic tool. Their Natural Armor is the toughest (Plate Armor). A choice for players who wish to be very non-human and alien.
2. Tidal: Their Natural Armor holds the middle ground in terms of hardness (Chain Mail). A choice for players who wish to be unique but still relate-able to near-humans, like Dwarves, Gnomes or Halflings.
3. Shallow: the most human-like of this folk. Their dorsal armor is slimmer and more flexible, allowing them greater mobility at the cost of less protection. While they still possess two sets of arms, the lower pair are almost completely vestigial: too small and weak to perform any arduous tasks beyond lifting small objects. Their faces are almost completely human except for their segmented irises and their mouths which, while closed, look small, but while opened completely split open the lower halves of their faces into long mandibles and maxilla “fingers”. Their hands, are slimmer and more flexible, allowing them to use human tools. Their Natural Armor is the least hard (Leather Armor). A good choice for players wanting to be very nearly human but visually different with minor differences to set themselves apart, like Elves, Half-Elves or Half-Orcs.
People of the Tides
As with the slow movement of the moons and tides, these people have profound ideologies around peaceful and deliberate lives. They rarely act hastily or without some deliberation beforehand.
Labyrinth Lord (or OSR game of choice)
As Dwarves, except replace their racial abilities with the following:
Their unique physique prevents them from being able to use weapons, armor or tools made for human use. However their limbs function perfectly for most tools needed for hammering, cutting, digging or scraping (they do not need tools for most tasks).
Armored Shell: Trilobites have a natural AC of 5 from the tough shells on their backs.
Amphibious: Trilobites can breathe equally well underwater as above land. However prolonged exposure to a dry environment will have consequences on their health. Reduce each of their saving throws by 1 for each entire day spent away from a body of water large enough for them to be fully immersed.
Armor Ball: Trilobites may roll up into a tough ball. This form makes them nearly invulnerable (Armor class of 4) and their movement speed of 150′(50′). However they cannot perform any actions except rolling around and smashing into things (attack as a war hammer, dealing 1d6 damage).