Doctor Renhol (played by Lisa Banes) was a Trill and a member of the Symbiosis Commission in the 24th Century.
In 2371 Renhol welcomed Jadzia Dax back to the grounds of the Commission's campus where she spent three years as an initiate. Unfortunately, Jadzia's homecoming was due to an un-diagnosed medical condition that threatened the Dax symbiont. Renhol initially prescribed injections meant to increase Jadzia's isoboromine levels. When this approach failed to halt the threat to the symbiont, Renhol wanted to remove Dax and join it with another host, knowing that this procedure would kill Jadzia.
Renhol's decision was not based on the medical needs of the case, however, but on her willingness to keep secret the fact that symbionts could be joined to a much wider segment of the population than was generally known. The symbiont was experiencing flashbacks as the result of the failure of a memory block, a block with the Commission had created in order to cover up the fact that the symbiont had at one time been joined with an unsuitable host, Joran Belar. Benjamin Sisko and Julian Bashir discovered Renhol's motives and threatened to expose the Commission's secret if eveything possible was not done to save Jadzia.
Renhol relented and Jadzia ultimately recovered after allowing the memory block to fail and Joran's memories of the joining to become part of her joined personality. (DS9: "Equilibrium")