Martyr Penitents

Am I blind or aren't there any rules for martyr penitents anymore? They do get mentioned in the Lore Primer and people online have been annoyed by MPs supposedly being restricted to the campaign but nowhere do I seem to find anything rules-wise about them. It even seems that way before the first official minis, some people were callint Ecclesiastic Prisonders Martyr Penitents – but that doesn't make sense because those haven't been brought back from the dead.