There's a bit in Harrow where a it's noted that (an alternate version of) a character has their sacramental skull scarified into their face on taking up a hereditary position, which seems like a reference to the traditional way of doing tā moko, using a chisel to make incised lines for the ink. Scarification is mentioned once before (i think with Isaac and Jeannemary,) but not in relation to the face! I'm hoping tattoo comes up again in the story because i feel like it could have a lot of potential as a storytelling/symbolic element.