The end game is to avoid legal consequences for their actions. These people don't understand the legal system and believe it works like an arcane magic system. If they send the right letters to the right people, they can make all their problems go away.

In this case, they believe there is a letter they can send someone that causes that person to owe them 1 gold bar per month unless that person performs some kind of action. This one sounds like it was sent to the New York State courts in an attempt to get them to drop legal action against them (or give them gold).

Searching "notice of liability" gets you a bunch of conspiracy theory websites with templates and instructions.