Kadec was a female Tigan, the Chancellor of Tigan for a brief period in 2364.
Kadec rose to power when the former Chancellor, Lomac was removed from power via the history altering tampering of a Tigan conspiracy which frequently rewrote Tigan history using the Tigan interface, a cybernetic implant ever Tigan had which connected them to the Tigan central computer, the store of all Tigan knowledge. Unfortunately, an away team from the USS Enterprise-D was on the planet at the time, and not being linked to the Tigan interface, were aware of the changes and uncovered the conspiracy. Kadec had the team put into custody, and had here fellow conspirator Edic work on reprogramming Data to forget the incident.
Shortly after Edic, realising the error of his ways, arrested Kadec for crimes against state, ending the conspiracy. (TNG comic: "History Lesson")