The Rhyn symbiont, a sentient vermiform lifeform, was born in 2105 in the Caves of Mak'ala on the planet Trill. Like all symbionts, it has the ability to be transferred from one humanoid Trill host to another, upon the death of the prior host. The symbionts take with it all of the memories of the previous Trill hosts so, upon joining, the new Trill host gains those memories. The Rhyn symbiont has had seven prior hosts, and is currently coexisting with its eighth host, Emery Rhyn.
Below is a list of the Rhyn symbiont's previous hosts, with relevant details of each host that Emery has "remembered."
- first host, joined in 2108
- second host, joined in 2166
- enjoyed grilled Bolian fintail
- third host, joined in 2219
- very popular composer
- enjoyed relaxing/composing in a bubblebath
- fourth host, joined in 2277
- fifth host, joined in 2302
- was a hobbyist botanist, and loved to grow her own flowers
- daughter Jalana was the grandmother of Dr. Isabel Pond, who ended up being a shipmate of Emery's on the USS Darwin-A.
- sixth host, joined in 2348
- Served with Phillipe Marquette on the USS Arcanus (NCC-67032), a Rigel class destroyer, as part of the 777th Tactical Wing during the Dominion War, under Captain Thomas Murchison.
- Raktajino was his favourite drink
- seventh host, joined in 2375
- Emery is the eighth and current host of the Rhyn symbiont, joined in 239301.
- Parents wanted her to be a doctor, joined Starfleet instead
- Was left handed until Joining, then became right-side dominant
- Has seasonal allergies (is allergic to pollen)