Coera

When the demigods or elves took Coera into their keeping, and shaped the emergence of life, they guided the evolution of plants and animals to create diversity and wonder, but also to create an animal in their image, both physically and mentally. This control over evolution extends far beyond the breeding practices used by people, and allowed for the creation of new species with features unlike those of their predecessors. After the creation of man and the barrier, when the majority of demis left Coera to create their own worlds, these secrets of evolution were hidden from man, so that he might live in a garden world or zoo world, instead of quickly pushing against the barrier and being overwhelmed by what was beyond. Of course, mankind develped mathematics and other technologies instead, so the handicapped forced an even more powerful adaptation.

Very few other worlds were given this restriction, so space travel, where it occurs outside of Coera, is accomplished in the innards of great beasts evolved for the purpose. Weaponry comes from "natural" sources. Libraries are as likely to be kept in an overdeveloped mind than on shelves, and radio and radar are replaced by telepathy.

The upside for humans is that it is very easy for them to adapt to and conquer the aliens, since their technology is far more adaptable than evolution, which at best typically takes several generations to produce replicable results. They have a great resource in math and science, and their services are in high demand on any world that does not consider their maths a heresy.