Howlers were predatory creatures indigenous to the moon Yavin 4. The origin of their designation comes from their hunting strategy: emitting a powerful howl capable of stunning their targets. These creatures bore a somewhat reptilian semblance. Although they typically moved using all four limbs, they occasionally adopted a bipedal stance for actions like charging, jumping, and attacking with their claws.
During the era known as the Hundred-Year Darkness, Sorzus Syn applied the term "howlers" to one of her alchemically engineered beings. Syn's research involving howlers, along with other alchemical constructs, ultimately resulted in the creation of the Leviathans.
In the year 14 ABY, after the Jedi Praxeum's transport ship suffered a malfunction on Yavin 4, both Jaden Korr and Rosh Penin encountered several howlers as they made their journey to the Massassi Temple.