Everyone destined to fall in loyalty with a Spark is born with that Spark’s sigil on their skin.
The scattering of trilobites among children born after the Heterodyne Boys vanish is taken throughout Europa as evidence that they’ll come back.
In Mechanicsburg all the children are still born with trilobites and that’s taken as hope of a different kind.
The scattering of winged castles throughout Europa is considered with puzzlement during the days when Wulfenbach is a small barony (which doesn’t even have an airforce!) and Klaus is mostly known as the Heterodyne Boys’ sidekick. Maybe it’s going to be someone else’s sigil?
Bang hides hers. She’s a pirate queen, the last thing she needs is to follow a Spark around. When she finds herself doing just that she hides the tattoo anyway. Gil would be smug and Klaus would be unsurprised.
Boris regards his with annoyance, he doesn’t want to belong to any Spark, and then with hope, it’s not the sigil of the Spark that experimented on him, he won’t belong to them forever, and finally with acceptance.
Moloch’s trilobite baffles him when he’s younger. If the Heterodyne Boys return it certainly won’t involve him. When he’s sent to Castle Heterodyne and sees the same mark on the other prisoners he thinks that’s it, the Castle owns them now and was obviously destined to. The truth, when he’s faced with it, scares him even worse.
Violetta’s trilobite nearly gets her killed. A sign of disloyalty in the making, written on her skin. Tarvek pulls strings to keep her alive and hopes it means a real Heterodyne (because the alternative is Lucrezia inhabiting the body of one and he will not see his stubborn, loving cousin in loyalty with her.)