Barbamon relates to Barbatos. The Purple symbol in the top pic is his sign. His sin is Greed and his celestial planet is Saturn.

Beelzebumon relates to the name Beelzebub another word for the devil although he is classifed as one of Lucifers assistants. The golden symbol in the top pic is his sign. His sin is Gluttony and his celesial planet is Venus.

Belphemon rrelates to the name of Belphegor. The Dark Blue symbol in the top pic is his sign He is rather lazy so no prizes for guessing his sin is Sloth and his celestial planet is Mars.

Demon the name pretty much says it all, name relating to a Demon Heritage. The Yellow Symbol in the top pic is his sign. His sin is Wrath, and his celestial planet is Jupiter.

Leviamon relates to the legendary name of Leviathan a supposed sea creature. He has also been assosiated as another of Lucifers assistants. The Light Blue symbol in the top pic is his sign. His Sin is Envy and his celestial planet is Mercury.

Lucemon Falldown Mode relates to Lucifer the Angel who rebelled against God and became the Devil. The Orange symbol in the top pic is his sign. His sin is Pride and his celestial solar relation is the Sun.

Lilithmon name relates to Lilith and was said the be Adam's first wife who went and adultered on him with Satan. The Green symbol in the top pic is her sign. Her sin is Lust and her celestial solar relation is the Moon.