Yes, there are spoilers here.
For both the comic and the film.
The issue is by Will Corona Pilgrim and Jorge Fornes. It starts with a woman, identified as a Dark Elf, in possession of an artifact of great power. Wong, Master of the Mystic Arts, is sent from Kamar-Taj to investigate. When the woman disappears with the staff, he returns to pull together other Masters of the Mystic Arts to help stop her. Those masters are Kaecilius, Tina Minoru, and Daniel Drumm.
I won't go into more of the story itself, but the players and the staff are the key.
The staff is likely the Eye of Agamotto, but odds are that it's also one of the two missing infinity stones.
The fact that Wong is a Master of the Mystic Arts and no just a man-servant is a nice move, but we see now that it's almost an order and not a specific title. We get four Masters here.
Kaecilius is not a name we've come across in Marvel before, but looking at the art it's pretty obvious this is the character that Mads Mikkelsen is playing. He already shows signs of arrogance and power lust. And just because we haven't heard the name before, doesn't mean it's the name he has at the end of the film or that he's not possessed by another force.
The other two Masters are also interesting. Daniel Drumm is Brother Voodoo in the comics and most Marvel fans will be geeked out if he appears in the film. The second is the mother of Nico Minoru / Sister Grimm who is part of the Runaways and A-Force.
A second issue of the prelude is coming out next month and is said to feature The Ancient One.