Barbatos is a duke who rules 30 legions of demons, is strongest in late April and when the sun is in Sagittarius, and for summoning he should be summoned during daytime with black candles, ivy, copper, and dirt.
He is a demon of communication, like some of his fellow demons, he tells the summoner of details concerning the past and future and has the power to mend broken relationships as well as create new ones. In particular, men and women in positions of power. These last two powers can be particularly powerful in combination where a person can not only befriend a person in power but also influence them toward their interests.
The communication powers don't stop there. Barbatos also has the power to give voices to animals, meaning that he can make it so that the conjurer understands what animals are trying to communicate to human beings. It is unlikely that this means the animals in question will actually speak in human language. More likely the demon Duke creates a sort of telepathic translator in order for humans to understand the thoughts being conveyed.
While there are other demons can also help lead the summoner to hidden treasure, Barbatos has the special ability to help the summoner find treasures that are hidden or via magical enchantment, Barbatos can magically unlock this for the conjurer.
Through the Latin word "barbatus" means "bearded", the demon Barbatos is not believed to have a beard in his "human" form, through he does have long, white hair and feathery white wings. When he appears to the summoner he comes with quite an entourage. Four "kings" and their troops follow him when he communicates with humans.
He was part of the 12 Orders of Angels - specifically the Order of Virtues. It is said that he still retains some sort of credentials with that group, through how this specifically works out is to say.