The contents of this page appears to be/is absent from all of the books made by Ernest Drake. Be wary of trusting its contents.
Draco Mortem, the death dragon, is much like the Basilisk. It is hard to study, due to the fact that it can not be seen, except in special circumstances. However these people in the circumstances are to have survived death, meaning that most dragonologists cannot see them. Fortunately for dragonologists, who have no intention of almost getting themselves killed, they also reveal themselves to the holders of The Death Arcana.
Another problem with trying to study them, is that they tend to live in remote places - occasionally caves but more often swamps and volcanoes. They are also believed to be the rarest of dragon breeds with only one existing at a time, however, as mentioned this is just speculation.
All these factors combine to mean that no adults have ever been found in the wild, although one dragonologist found an egg which appeared to have been abandoned and watched it hatch and grow before releasing it before it was fully grown. The egg was deep black with lime green glow.
No one is sure how they began.