Astaroth and Beelzebub are a Great Dukes of Hell, the strongest demons in Hell hierarchy. Dukes of hell are a rare breed, directly created from Lucifer's grace as a mock up for Chuck making the archangels out of his own divinity, that's what makes them so powerful and an absolutely terrifying evil force. There is only a couple Dukes of hell and those are Astaroth and Beelzebub, being Lucifer's right and left hand respectively, being the tree of them part of The Evil Trinity.
Astaroth's true form is a depicted as a nude man with feathered wings (as a mock to God's angels), wearing a crown, holding a serpent in one hand, and riding an infernal dragon. He seduces by means of laziness, self-doubt and overthinking. In the latest millenia, His way of claiming souls for hell is to plant the seed of mental illness in humans and let them slowly get consumed by depression and anxiety, only to come offer them peace of mind with a deal of the usual 10 years where the humans will get their life immediately fixed in exchange for their souls. It’s highly effective.
Beelzebub’s true form is quite similar, a nude man with feathery wings holding a spear, though in some depictions he’s seen in a more infernal look, demon wings being bat-like and holding a bow. His temptation comes in the shape of gluttony, pride and false idolatry. His way of tempting souls is to infuse these sins into their hearts, giving them everything they want til the point it consumes them and brings them chaos and hurt around those they love. If any of his tempted souls attempts to seek for redemption, he presents to them like with a miracle solution, and deceives them into thinking he’s God or a similar deity, offering them redemption in the form of a contract. Without knowing it, those humans are signing their souls to hell, and not to heaven.
Astaroth and Beelzebub only respond to Lucifer ( @unholybcnes ) and they are his most loyal demons.