The pumpeters are mysterious skeletons whose pumpets (a more complicated trumpet) can summon forth great maladies. The ultimate pumpeter, Isapumpa, is said to be able to end life with one blow and awaken all life on Pumpment Day with the second blow. The pumpet's sounds are similar to that of the recorder if a person were to stick a soggy bag of potato chips into it. Pumpeters are known across the world for being very bad omens, so many adventurers, upon spotting one, will immediately try to kill it. Upon defeating pumpeters, adventurers are usually welcomed with a mysterious pumpet's tune, signifying that the pumpeter has yet to stop pumpeting.

According to Certain Canon, the pumpeters are said to sound their pumpets during the apocalypse, implying that the apocalypse has been an ongoing phenomenon for all of recorded history. Many scholars tend to agree with the Certain Canon, taking into account 1) that all of the skeletons on G-Urth probably number the same for the total population of the dead, 2) the various demons who have infested the continents, and 3) the fact that Peklo exists. Some conspiracy theorists argue that it cannot be known if the apocalypse has already happened, because G-Urth is, by its nature, the land of death and suffering, and if the apocalypse is supposed to turn the G-Urth into that, Certain Canon must mean something much more grimmer.

Pumpeters possess highly dangerous attacks, such as Horn of Fate, which has a high chance to kill an entire party of adventurers with food poisoning and the Pumper Plague. Pumpeters are immune to both ailments, preventing the attack from hitting themselves. Another pumpeter attack is Hostile Terror, wherein the pumpeter will disrobe while playing familiar hentay tunes from the Bank of Anime Music. Unlike other demons, pumpeter cannot be recruited through negotiation, and instead has a unique response when talked to. Usually, a pumpeter's response is a rendition of Careless Whisper.