The DC Universe is composed of a number of different dimensional planes, most notably parallel Earths (see Multiverse), but the latter were eliminated when reality was altered by the Anti-Monitor (although stories featuring parallel Earths have continued to crop up with various rationalizations in the following years). Other types of dimensions still exist, however, including the Antimatter Universe of Qward, the Pax dimension, the Fifth Dimension and the Bleed. Prison dimensions, such as the Phantom Zone, are meant to house superpowered criminals who are too powerful for any conventional means of containment. Dimensions make up many universes, of which some are created and destroyed with help from supernatural forces and elements from which power is drawn. As well, certain dimensions function as crossover opportunities for heroes from different comic book companies to interact, either from competing companies, or from companies absorbed by competitors. The most notable example of the first kind of crossover has been between DC Comics and Marvel Comics, and the latter with Wildstorm Comics. An example of the latter kind of crossover would be DC's acquisition of Fawcett Comics, Quality Comics, and Charlton Comics and the absorption into the DC continuity of the original Captain Marvel, Plastic Man and Captain Atom. In this way, heroes originally published by different companies are now part of the same fictional universe, and interactions between such characters are no longer considered intercompany crossovers.