They're not stupid, they just aren't meant to be here and they're having a hard time with that.
Goblinoids are a group of related non-natural creatures that do not arise from evolution but rather, like kobolds and dwarves, are products of magical creation. When a dream engine is destroyed the residual magical effect this has alters local magic in a way that can result in spontaneous generation over time. Usually this occurs within a decade of the engine's destruction if it is going to happen at all, with the chance of spontaneous generation being higher if multiple engines are destroyed within a ten year span.
They're goblins, you kinda know what that is already.
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The change in local magic that can cause them to spawn is a result of how dream engines work. They employ the use of narrative magic and when they are destroyed this magic lingers for a time and serves to change the environment slightly in a manner akin to a small change in genre. If this change is significant enough, and if enough other uncountable factors are favorable, then spontaneous generation occurs.
Physically goblins are the most human-like of all the races, having largely the same general anatomy. This means that, like humans, their tolerance for various climates is rather broad. Unlike humans though they are far less tolerant of cold climates and on colder worlds they will tend to die out if they are not "adopted" by a local community who can teach them or provide tools for surviving in the cold weather.
Further differences include their ears, which are pointed at the ends, are much longer than humans, and are able to be independently moved in a manner akin to animals such as dogs and cats. Their eyes and mouths take up a larger portion of their face than humans, their skin ranges from green to yellow, they have only three digits on their hands, and only two digits on their feet. Beyond those outward differences they also have a multi-chambered stomach and several sets of bones are shaped differently. Their hips and tailbone are very different- while human tailbones show signs of once supporting a tail goblin tailbones do not show any vestigial structures here at all. This pattern holds true for them over all of their anatomy as they do not have any vestigial organs or features. There is significant anatomical difference between goblins in various locations however, owing to their spawning from wild magics, but the previously noted characteristics tend to hold true across all observed instances of golbinoid populations.
Goblinoids make up accepted members of many settlements and are generally not considered noteworthy. There are places where wild goblin populations exist that have neither made any attempt to join an existing settlement and where no existing settlement has attempted to invite them to live in the settlement. These wild goblin populations have mixed reputations. In some places they are considered vermin while in others they are not disliked but are not interfered with out of a desire to protect their developing cultures. Overall though most places simply do not have goblin populations, wild or otherwise, and opinions on them tend to be based on ignorance as a result. Wild goblins are generally considered environmentally disruptive and are seen as an ill omen due to their association with the machines of war who's destruction creates them. However, since the Azi'ani first began accepting goblinoids among their congregation many nimbus cities and cosmopolitan disks that would otherwise have never interacted with goblinoids have begun to have regular interactions with them, leading more places to have a less racist opinion of goblinoids generally.