Dictionnaire Infernal – Collin de Plancy (1863) (paraphrased)
Picollus was revered by the ancient inhabitants of Prussia. He was offered the head of a dead man and a tallow was burned in his honor. He would appear to important people during their last days. If he was not appeased, he would appear a second and finally a third time, when only human blood would mollify him.

Peckols and Patollo (known under a multitude of different names) were gods in the pagan Prussian mythology worshiped by the Old Prussians. Most researches believe that despite varying names, Peckols and Patollo were the same god in charge of the underworld and the dead. It is usually described as an angry, evil spirit similar to Lithuanian velnias.[1] Hungarian Pokol also means the Underworld.

Patollu was first mentioned in 1418 by Bishop of Warmia in a letter to the Pope. Chronicler Simon Grunau (1529) provided more vivid but dubious details about Patollo. According to Grunau, Patollo was one of the three gods portrayed on the flag and coat of arms of King Widewuto and worshiped in the temple of Rickoyoto. He was portrayed as an old man with white beard and white headdress similar to a turban. He was a scary and ruthless god of the dead. He would haunt and taunt the living if they disobeyed their pagan priests or buried the dead without proper sacrifices to the gods. Many other medieval writers, including Alexander Guagnini and Lucas David, followed Grunau in descriptions of Patollo.

The Sudovian Book (1520s), mentioned two beings – Peckols, god of hell and darkness, and Pockols, airborne spirit or devil.[1] The same pair is also found in the church decrees of 1530 (Constitutiones Synodales). There Pecols was identified with Roman god of the underworld Pluto and Pocols with deities of anger Furies. Jan Sandecki Malecki followed the Sudovian Book and wrote about Pocclum and Poccollum. Jonas Bretkūnas, Caspar Hennenberger, and later authors attempted to reconcile the accounts provided by Grunau and the Sudovian Book. In the 17th century Christoph Hartknoch and Matthäus Prätorius testified that people still believed in Picolli and Pykullis.