The 71st spirit of the Goetia and a Duke of Hell. He appears as a man with a large number of different faces, resembling both men and women, and holds a book in his right hand. His office is to teach all arts and sciences to anyone and to declare the secret agreements of anyone. He knows the thoughts of all men and women and can change them as he pleases at will. He can also cause the love of a person for another and show a person to the summoner no matter what part of the world that they are in. He governs over 36 legions of infernal spirits.
"One of the 72 demons of the Goetia. He is a duke with many faces that change constantly. He holds a heavy book in his right hand which has the thoughts of all living beings, past, present and future, written in a language only he can read."
—Shin Megami Tensei: Strange Journey Compendium
They are mainly found on Eridanus Sector as a random encounter at the 2nd and 3rd floors. There is a Dantalion NPC on the west side of the top floor of Eridanus, reached after getting the Gate Search C from Ryan. It gives the side-quest "Tales of Investigation" and regularly will employ the protagonist to be his proxy explorer across the Schwarzwelt, paying him to fully map several floors of each Sector. Once every Sector has been fully mapped, he will gratefully hand over a cache of Incenses to the protagonist.
Known as Dantalian, he appears in the New Game Plus Challenge Quest, Slay the Demon in Hiding. Talking to the Baker at the Bakery in Mikado Castle has him state his desire to learn more. He will transform into Dantalian, telling Flynn that he doesn't care if he becomes a demon as long as he learns. In the battle, Dantalian's personality surfaces, saying that those who seek to learn become nourishment for him and in turn have their wishes granted. During the battle his face becomes the Baker's, and asks Flynn to stop, as he only wants to learn. This is a trap and agreeing will have Dantalian call Flynn a fool. The demon is surprised at his defeat, unable to understand how even with his infinite knowledge that he could be defeated by a mere human. Dantalian's final words are in the Baker's voice, asking if it's so wrong to want to know.
Dantalion, a demon who mocks humanity's materialism, is fought in the Museum. He petrifies Rei Reiho and takes her to a room across where Dantalion is fought. During the battle against Dantalion, the protagonist can stun him for three turns by using the art he can take from the museum.
"One of the 72 demons of the Ars Goetia. He is a powerful Great Duke of Hell, with the ability to change his face into that of all men and women. In his hand is heavy (sic) book that only he can read, within which is written the past, present, and future thoughts of all living things."
—Devil Survivor 2 Compendium
Part of the first SpotPass group of demons, Dantalian is a special fusion requiring Orcus and Toubyou.