
We see that the Fiends were created by human magic users around the year 12,000 BC. By the year 600 AD, they were the only magic users left and declared war on humanity. They lost that war, but they were still around in 1000 AD. However, we do not see any fiends, besides Belthasar's assistant, in the year 2300 AD, and we don't really see any in the year 1999 either. So did the fiends die off sometime between 1000 and 1999, or were they killed when Lavos attacked in 1999?