Celeste Weaver is one of the reincarnations of Ah Ray In

There are three incarnations of Ah Ray in in total that we know about. One is Ah Ray In.

Two is Prophetess her sister 1 million years into the future on New Deva (which is likely a re-terraformed Earth with much more water.

Three: is Celeste Weaver who grows up on a planet where all religions are banned. You can still believe in God but because of religious wars on planets the settlers came from they banned all organized prayer groups of any kind. However, you are still allowed to pray with your family in your homes or quietly anywhere, just not allowed to build any churches or organize anything into a church.
If you don't like this you can move to another planet I guess. So, Celeste grows up believing in God pretty much but not religion.

When Ah Ray IN is martyred on Isfahel (likely a re-terraformed Mars 1 million years into the future, Prophetess is born as her sister retroactively who is the same age as Arcane on New Deva. So, even though Arcane is betrothed to Ah Ray In who is a New Devan Saint when she is tortured to death on the planet Isfahel by the leader there, retroactively Prophetess is born caused by the prayers of the faithful praying for Ah Ray In after she is martyred.

So, both Ah Ray In and Prophetess are sisters and know each other growing up on the planet New Deva. They meet Celeste at some point also somewhere in Chapters 12 through 18 of Memories when she is married to Arcane and has two children and they are visiting the future on New Deva.