We are born with them. Many do not know they exist. Only the Nexus and few other worlds have record of Natures or a way to pinpoint what a person's Nature is. Most are not powerful enough to be noteworthy, but there is only one at a time that could have Tethering, Separation, or Destruction.

[They have an easy explanation they've relied upon before for this.]

Many worlds have a concept of nature vs. nurture in a person, and what that means for their personality, values, and growth. This doesn't discount nurture, but Natures are a clean label for the literal nature of a person. Breaking a person down to their very base, inherited nature, before life experience interferes.