Summon: Daytime, yellow candles, tin, fire, chickory
In the ranks of demons, "President" does not mean the leader of a nation as is most commonly used today. Rather, each demon President is the leader of a social, educational, or political group. In the case of Marbas, the title of President refers to his role as the head of the schools of mechanics and engineering.
Many of the 72 Goetic demons teach something, but Marbas (also known by the name "Barbas") is one of the few who are focused strictly on mechanical engineering and its subordinate teachings. Those who summon him may be imparted great wisdom of a technical nature, as it is believed that his knowledge of the subject far exceeds the most brilliant technical minds of humankind.
One might expect such a scientific mind to be limited to scientific pursuits, but Marbas is far more than just a scientist. He will answer truthfully to questions asked about the secrets of others, and has been known to heal diseases upon request (as well as cause them). The demon President also has a highly sought after ability that few other demons share - he can cause humans to shapeshift into other forms.
Now before you get too excited (werewolf fanatics, I'm talking to you), he does not give humans the power to shapeshift, he can simply cause a shapeshifting to take place. Whether or not he will be willing to change one back to their original form is entirely dependent on him.
Marbas first appears to the summoner in his demon form, which is that of a large and ferocious lion, but he will change shape into his human form if requested. Those who have summoned him have reported that he is of average height with brown eyes and black hair.