It is important to recognise that Buddhist thought does not propose the transmigration of souls – this is a common misunderstanding of Buddhism; that if you live a bad life you’ll return as something ‘lower’ like an animal or insect. Reincarnation simply implies that at the point of rebirth one would be promoted or demoted across the ten realms of existence.
“At the top is Buddha (Nirvana) and the scale descends as follows: Bodhisattva (an enlightened being destined to be a Buddha, but purposely remaining on earth to teach others), Pratyeka Buddha (a Buddha for himself), Sravka (direct disciple of Buddha), heavenly beings (superhuman [angels?]), human beings, Asura (fighting spirits), beasts, Preta (hungry ghosts), and depraved men (hellish beings).” http://www.buddhanet.net/e-learning/reincarnation.htm
In Catholic teaching, after death the soul must rest for a while in purgatory in order to be purified enough to achieve the holiness to enter Heaven. This was a pretty powerful tool for extracting money from adherents for a speedy and pain free time after death.
The Egg, an online story written by Andy Weir, has become a viral phenomenon. It takes aspects of many major world religions and combines them into a haunting and thought-provoking hypothesis. That everything forms part of ‘the only one’ – together. This concept has become a major lyric theme for Circularity across many songs. A short film was adapted from the idea, with a soundtrack composed by Nils Frahm.