The Archdemon, formerly known as Bullwong, Winged Demon and ArcDemon; is a recurrent monster in the Dragon Quest series and was introduced in Dragon Quest II.
Equipped with almost everything you can think of on a stereotypical demon bears wings, horns, a spiked tail, and a pitchfork. With stats to match its bulky purple body, these monsters are usually a force to be reckoned with; capable of dealing heavy physical hits, but also casting advanced offensive magics to destroy its opponents.
Belial (formerly Zarlox) is a miniboss from Dragon Quest II and a recurring common monster in the later games. It is a more powerful version of an archdemon and the last in a trio of bosses players must face as they climb Hargon's tower.
A general in the army of the underworld. Already powerful in its own right, after psyching up its attacks can injure entire parties with a single strike.
Belial is the name for the Christian and Jewish devil in the original Hebrew bible.
Trivia
The Archdemon makes a cameo in the Tenshinhan/Tien Shinhan saga of Dragon Ball, which is also created by Akira Toriyama, who is the designer of the Dragon Quest series. It tries to enter the Tenkaichi Budokai but is defeated at the preliminaries.