Roper

Ropers (ローパー) are a heteromorphic race of beings from YGGDRASIL.

Background
There is very little information on Ropers, though what is known is that there is a subspecies known as Herdropers.

Abilities
According to the Narberal Activity Report, a Roper's fluid is some kind of powerful secret drug.

Trivia

 * Ropers are officially introduced in the Light Novels in the Overlord Bonus Volume.
 * According to the author, one of the Five Worst is a Roper-type monster.