Does Cortazar use an archetype or magic realism to develop the theme of "House Taken Over"?
"Casa Tomada", or "House Taken Over, by Julio Cortázar is a representative of magical realism because the plot of the story can only be moved forward by the use of dynamics that are sustained by supernatural or magical intervention.
This means that the author has free literary license to create characters and situations which are outside of the norm, and whose traits color the story even further. In Cortázar's case, he does use archetypes as his main characters; it is indeed his use of archetypes what moves the theme more effectively.
When analyzing the characters of Irene and the narrator, we do see the archetypes of the Gothic genre: two potentially disturbed individuals who have allowed life and fate to lead them, instead of them leading their own lives. They are isolated, seem quite tragic despite of living presumably "well", and suffer from the same kind of phobia. Hence, the themes of isolation, desolation, creeping insanity and mundane compulsion define the characters of Irene and the narrator, while effectively matching them to their surroundings, and to their immediate situation.
As a lonely pair of siblings, they have confined themselves to a house and to a routine of which little color or character actually come out. When they begin to hear "the noises" take over the different parts of the house, their tendency to routine is so strong that they simply move into another specific niche within the house where the noise had yet not caught up with them. Once the noise does enter their separate quarter, and the house is completely "taken over", the brother and sister will merely follow each other's lead of leaving the house for good and throwing the keys to the house in the sewer.
The actions of the two leave a lot to the imagination, as well as the enigma of the noises in the house. However, this is the whole purpose of the story: to infer from the few cues given by the author on what exactly is going on in the house, or in the minds of the main characters. This is also archetypal of Gothic literature, as there is always a "perennial" mystery, curse, or situation permeating the plot.
Conclusively, Cortázar does use a Gothic archetype in his type of characters and in the stylistic devices of the story in order to convey the themes effectively.