Hooray for bad thread names.
This thread should be called Dept Heaven relationships. This way, people would know what the thread is about without having to read the whole thread.
KitN: Avenheim castle (the setting) is "somewhere between heaven and the underworld" according to the Sting intro movie.
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In Riviera and Yggdra, there is a place called Heaven's Gate. There are some references to the underworld (Utgard) in Riviera.
There are no characters common to both Riviera and Yggdra.
KitN has some characters in common to both Riviera and Yggdra.