The bulezau first appeared second edition for the Planescape setting in Planescape Monstrous Compendium Appendix II (1995).
The bulezau appears third edition in Dragon, in issue #341 (March 2006) in the "Demonomicon of Iggwilv" feature. The bulezau was also detailed in the Fiendish Codex I: Hordes of the Abyss (2006).
The bulezau appeared in fourth edition in Demonomicon (2010).
Bulezaus are the core of the heavy infantry of the armies of the Abyss. Bulezaus have the shape of a big man with the head of a ram. Despite their appearance they are good warriors, particularly in melee combat. They aggregate in groups only if they have a powerful leader able to control them; whenever this leader passes away, it is almost certain that bulezaus will start to fight each other until death.