Mortar

The Mortar virus is a highly lethal disease. Nobody knows where the disease came from or who created it. However, some people suspect that it was made by the Lord of Vampires (aka Valtor) or the Lord of the Fortise (aka Eric Blythe) to eliminate the Lupis and the Halcyons, but it accidentally went out of control and started to spread across other races.

Victims
It first infected the Halcyons and the Lupis, but it spreaded across the Fortis people and the vampires as well. None of these four races were capable of healing themselves from the disease, which resulted in countless deaths. However, there are people that survived the plague and they assembled and flew to a new place where they're rebuilding their races.

Remedies
There are a few races that can heal the disease. All of these are categorized in the Rare Races section (because they're rare, as the title says). Almost nobody knows where they live.

Fairies
Fairies are one of them. Their wings have great healing powers, but if a fairy heals you personally, the process is a lot safer and quicker.

Merpeople
The scrubs of a mermaid or merman are an option too, but for a powerful disease as the Mortal virus, you would need all of the scrubs of around ten merpeople. Just like the fairies, if a merman or mermaid is personally healing you, it'll be safer and quicker.

Healers
There is one last way to be healed, but it's very hard. There are some healers (they can be from any race) that are extremely talented. Healers with that amount of talent are born around once in ten thousand years.