Sometimes, it’s useful to be able to swap around similar features from different classes, such as using oracle mysteries as cleric domains. You might want to have different kinds of clerics for various concepts (perhaps Merothian clerics of Community focus on the founders of each community, so they use the Ancestry mystery as one of their domains). Sometimes you might want to expand options for some other form of 3pp (such as Sigil Scions).

In any case, this specific swap is pretty straightforward.

Mystery spells replace the domain spells of the same spell level. They use the domain spell rules. This does mean a cleric taking a mystery gains access to its mystery spells on character level earlier than an oracle. That’s fine.

Then the cleric gains two revelation powers, one at 1st level, and one at 8th level. A GM can assign these revelations (for example, perhaps all clerics who take the ancestry mystery as a domain gain blood of heroes at 1st level, and wisdom of the ancestors at 8th level), or allow clerics to pick them, but either way they must be revelations can be selected by an oracle at 1st and 8th level. Any calculation in a revelation that works off the character’s Charisma instead works off the cleric’s Wisdom.

And you’re done!

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