Comus is a short masque, wherein players players sing and dance in honor of some celebratory event in the life of the noble family that sponsored the masque. Its origins were in a folk tradition wherein players wore actual masks, but by the 1600s, the masks were dropped from the masque performances. Singing and speaking parts were played by professionals while courtiers took the non-speaking role. In accord with one of the masque conventions, Comus presents an ethical debate instead of a masque pastoral or fable. It was first performed at Ludlow Castle for the Earl of Bridgewater on September 29, 1634 and published later in 1637.
The Tempest is a a full length five act play that is one of the harder of Shakespeare's plays to categorize. It is one of his romances and has elements of comedy, with a successful romance, as well as elements of tragedy and the "problem play." The last of his plays to be performed onstage, it was written c. 1610-1611. Professional players performed it onstage. Some elements of the play never reach satisfactory resolution at the end. The theme of this play is the large philosophical one of the nature of humanity. The thematic elements that illustrate this are the questions of differentiating reality from illusion while choosing between crude primitive values or the riches of art and civilized values.
The two plays are very different on this structural points yet there are similarities in the thematic elements of transformation and magic. In both plays, characters are magical and can create illusions even to the point of transforming themselves or even transforming others. In Comus, both an evil character and a beneficent one can transform themselves, though Comus, the evil Bacchanal character, is seemingly the only one who can transform others; the Attendant Spirit seemingly cannot transform others, only himself.
How many goodly creatures are there here!
How beauteous mankind is! O brave new world
That has such people in't!
(The Tempest, V.i.)