Star Trek: 10 MORE Alien Encounters Before First Contact
7. Romulans
The Romulans aren't quite as prolific as their Vulcan cousins when it comes to human history, but they are by no means absent. Alternate histories and timelines see them delaying human developments, such as Agent Sera in Tomorrow And Tomorrow And Tomorrow, but this entry is dedicated to Tallinn, the Romulan Supervisor.
Her assignment, to protect and aid Reneé Picard, sees her hiding in plain sight, on Earth, in the early 21st Century. It takes another alien visitor to find her (more on that later) but when she and Jean-Luc Picard do meet, they quickly learn to trust one another. Having Tallinn played by Orla Brady certainly helped.
The Supervisors for whom she works had previously intervened in human affairs (thanks, Gary Seven!) and are primarily tasked with ensuring history plays out the way that it should, without interference. Tallinn, a Romulan, is something of a ray of hope as well. If Sera represented the Romulans working to harm humanity, then surely the existence of Tallinn proves that there are still those who would wish to see it thrive.