"They do not fully understand what death is and this makes them dangerous to be around. In the culture of the Heralds, each being is made of many kinds of interacting life. They live and die in a cacophony of birth and death, fading and renewing all the time. They are a colony of things. They assume that everybody is.
"If someone dies around a Herald, they will keep speaking, addressing the microfauna consuming the corpse from within. If not prevented or advised otherwise, the Herald will 'garden' all the forms of life upon the corpse into a coherent whole, inhabiting the old form. It is the polite thing to do. Like helping someone who falls sick at your home, or offering new clothes to someone who has spilt their soup. They will educate this colony of things in how to consume the remaining chemical memories of its former host, how to walk in its body, then politely let it go. This may take time...
"Though the Heralds are by no means evil things, they are so alien and strange that to most people they may as well be. They prefer to deal with intelligent undead, or other very long-lived and indifferent individuals. Unprejudiced. The surface as a whole is strange to them. They value calm, politeness, and a discreet hand. You can never be sure how someone will react..."
-Trench Heralds, from "Fire on the Velvet Horizon"