Having one of many possible combinations of races for parents, the only common visible trait among Crosses is that there are no common visible traits among them. Even if two Crosses have the same parents, the two would likely differ greatly: one child from the same Coyote and Dingo parents, for example, would look more or less like one of its parents than its siblings probably would, and more extreme Crosses, such as those from a Ye'en and Feline, would be likewise even more unique.
The only other trait all Crosses share is their incompatibility with other races. A Cross can only ever have offspring with one of its component races, and even then Crosses suffer from reduced fertility. This, in addition to their rarity in the first place, is another reason why Aesira is almost completely composed of pure members of each race. The actual likelihood of a particular Cross appearing is somewhat easier to estimate when each race's sexual practices are taken into account, explained here.
X = Can hybridize.
[Blank] = Cannot hybridize.
S = See explanations below.
Special Cases Edit
Sa'ern Cross-Breeding Edit
Seaborn Cross-Breeding Edit
Ye'en/White One Cross-Breeding Edit
During the early years of the White One subrace, any union between a Ye'en and a White One that produced offspring only ever produced pure White One offspring: Crosses could not happen, and did not for quite some time even after there was the possibility.
Reptus Cross-Breeding Edit
The Serpentkind and Lizardkind are unique among the races on this list, as they are actually comprised of an even smaller subgroup, of the different species of snakes and lizards. These species can interbreed with each other, but with nothing else. Cobras can crossbreed with Boas, but not with anything else outside the Serpentkind race.
Ritualism Retcon Edit
It should be noted that as the art of Ritualism magic is capable of causing almost any effect, so long as the Ritualist is willing to invest an appropriate material and preparation cost, using the magic to change an individual's physical state (and by extension, their genetic compatibility) is completely possible, but extremely risky, costly, and difficult.
[work in progress]
While they have always been allies, Ye'en and Dingo do not produce many Cross offspring, as they only occasionally meet at all when some members of one race come to each other's land for whatever reason. When a Cross does result from a Ye'en and Dingo pairing, it is viewed as a very good event, as it reinforces the bond between their cultures. Typically, the visiting parent stays with the other parent's culture from that point on: a Dingo on Ye'en stays there, and a Ye'en on the Silver Isles does likewise. Ye'en refer to Crosses as oa ye'en, "of both homelands."