There are many accounts of the aeldreans physical appearance, but they were shapeshifters and it's unknown what their true appearance was. Their origins have been hotly debated. People consider them gods, angels, demons, or aliens.
They appeared thousands of years ago and disappeared without a trace within a hundred years. The only evidence the aeldreans ever visited Asmoria is the children they left behind.
Aeldring are the immortal descendants of the aeldreans. The first generation appeared as miracle pregnancies, the children appearing as almost perfect clones of the parent that carried them. Later generations are produced in the usual way.
While aeldring are shapeshifters, their main form is set when they first shift. First shifts occur later in life in later generations. First generation aeldrings may have shifted as a teenager while by the third generation shifting began to occur in early adulthood. Around the sixth generation, some aeldrings never shifted and died as mortals.
Shifting is a difficult task for the aeldring and it only gets harder as the generations go on. The most talented shifters can hold an alternate form for several hours while unpracticed individuals may only be able to hold a form for minutes. They can only shift into living forms and immediately revert to base form if they fall unconscious.
After shifting, there is no way to truly kill an aeldring. They can never bleed out due to their ability to infinitely generate blood cells. Removed limbs can be reattached and will reconnect nerves with a little patience. They cannot burn to death, as their cells cannot be altered without their consent.