Sonja is a fictional character from the Underworld series of films. This character is the daughter of the vampire elder Viktor, introduced by flashback, in Underworld. Red Sonja, the She-Devil with a Sword, is a fictional character who first appeared in Conan the Barbarian #23 (Marvel Comics).
tetralogy (plural tetralogies) 1  A set of four works of art that are connected, and that can be seen either as a single work or as four individual works. They are commonly found in literature, film, or video games. ( 2 medicine) A combination of four symptoms.
From Wikipedia: Tetralogy of Fallot (TOF) is a congenital heart defect which is classically understood to involve four anatomical abnormalities (although only three of them are always present). It is the most common cyanotic heart defect, representing 55-70%, and the most common cause of blue baby syndrome..