The Pastenture is a Universe that exists in the past, present, and future.
The pastenture is considered as a Multiversal, and sometimes Omniversal, anomaly, due to it likely requiring universes inside of universes. The Pastenture is also known for its characteristic to fluctuate in size, being as small as the distance between two stars, and can be as big as several Universes.
The Pastenture is capable is destroying Omniverses, by destroying itself while it is unfathomably large, tearing holes across time and space across a large distance.
Pastentures can only occur if time is dilated to a extent larger than the Universe being tested, that is why pastentures can be any size. Time dilation large and powerful enough to cause a pastenture can only occur when a Multiverse is a billionth of a billionth of a billionth... of a fraction of a second old, when time is "broken" due to the power of the explosion of the birth of a Mmultiverse. This means that almost all Multiverses do not have a singe pastenture, but an extremely small percent of Multiverses who have pastentures are almost completely made of them, this is what makes pastentures unknown, due to its rarity.