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 they exist in both YGGDRASIL and the New World. In addition there is a subspecies known as Herdropers that possess a hive mind.

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.