Chimeras are genetic hybrids, creatures that possess genetic material from at least two separate entities. Legend has it, the first chimera was Chimera herself, the divine daughter of the Greek gods Typhon and Echidna. She possessed both the body and head of a lion, but her tail was a snake. Attached to that snake, there was a goat head that breathed fire. Greek legend says that the hero Bellerophon- the son of Poseidon- slayed Chimera while riding the winged-horse Pegasus, his trusted steed, into battle.
While Chimera was the offspring of two deities, she wasn’t a deity herself. Instead, she was a monster. A monster so fearsome to look upon that even catching a glance of her was said to be an omen of great misfortune. Chimera often appeared before extreme disaster hit – she was an omen of storms. Earthquakes, tornadoes, typhoons, tsunamis, hurricanes, landfalls, hailstorms, floods, blizzards, volcanoes, wildfires – she would appear before any of these hit, if the storm in question was going to be devastating in scope.
She would also appear where devastating droughts would occur. If a famine was going to cause a great deal of destruction, Chimera may have been spotted before it. But it wasn’t just natural disasters that Chimera would appear before. No, she would also appear before the tempests that humanity set into motion. It may have been possible to glimpse her before a war would start, before a genocide. She may have been present in the moments before the Holocaust was set into motion. As an omen, her appearance was indicative of the worst fortune of all.
Outside of Greek legend, chimeras are typically supernatural creatures that are hybrids. Some of them are also able to create hybrids of their own. Chimeras are typically powerful, able to fully utilize the strengths of all the genetic material spliced together in their bodies. While it may be possible for a chimera to share the genetic material of a shapeshifter and therefore be a de facto shapeshifter, chimeras do not inherently possess the abilities of a shapeshifter (which is a common misunderstanding).
In a real-world context, chimeras are genetic hybrids. Human chimeras exist in specific situations. One such instance is when there are two fetuses in the womb, and one fetus absorbs the other. In such a situation, the fetus who absorbed the twin fetus becomes a chimera. The genetic material of the absorbed twin fetus is added to the genetic material of the non-absorbed twin fetus, making the resulting fetus into a chimera.