Dragons of the dead. They are powerful dragons that are difficult to kill, the used to formerly exist in Transylvania but were destroyed when the modernizing of the world came about. It was during Vlad's reign that the Dracolich came to existence, using the bodies of slain dragons to do his bidding. His reign ended in 1476 when Vlad the 3rd died, his location and how he died was unknown, but it was said his body was cut to pieces. And, along with him went the Dracolich.
Since 1476 there have been no Dracoliches, nor do many dragons wish to bring back the deceased. While necromancy is a practiced art, dragons that practice this try to respect the permanently deceased.