Lakksis was invented by a Thetran named Korriklimm. His programming included an ability to learn from his experiences, but he could not extrapolate from them. He was also programmed to give tourists visiting Nestra whatever they wanted.
Lakksis met the Sixth Doctor and Janis Carma when both arrived on Nestra independently investigating reports of missing vacationers. Lakksis had indulged vacationers in whatever they wanted, and when they became sick, sent them to the infirmary. He didn't provide them with the care they needed, however, because it involved giving them something unpleasant, which went against his programming.
After he had captured the Doctor and Janis, the Doctor explained to him that sometimes people need things that are unpleasant, like medicine or healthy food. Lakksis seemed to appreciate this information, but before he could put it into use, Janis blasted his head off.