Scarlet Slayers are dragons with strong hypnotizing abilities; similar to that of the Drago Menta.
A Scarlet Slayer appeared in "Porkfester's Pigfarm Island". According to Gwizdo's Dragonpedia, they are easy to hunt because they are fat, and hate water.
Shedding Scarlet Slayers mostly hide themselves anywhere they can manage, possessing nearby creatures to give it food. Shedding Scarlet Slayers look much different to the actual dragon, with many tentacles on its body. These "tentacles" have red eye-like orbs on them, which fly out and possess nearby creatures.
Similar to the Drago Menta and Petrovile, a possessed individual can be "cured" with water. (Or in the Drago Menta's case; ice/snow) The Scarlet Slayer itself is weak to water, as it burns away the Slayer's skin like acid.