Tregonsee is a Rigellian from Rigel IV, possessing a barrel-shaped body without visible sensory organs, multiple tentacles, and four blocky legs. This species innately senses its surroundings through perception, interacting spatially without sight or hearing, an ability highly effective in environments like Trenco's distorted ether. Rigellians are naturally telepathic, a trait amplified when Tregonsee became a Lensman.

Serving in the Galactic Patrol, Tregonsee initially commanded the wandering base on the tempestuous planet Trenco, critical for thionite interdiction. There, Tregonsee provided vital support, including supplying a replacement Bergenholm unit to fellow Lensman Kimball Kinnison.

Selected for advanced Arisian training, Tregonsee ascended to Second Stage Lensman alongside Kinnison, Worsel, and Nadreck, gaining augmented mental capabilities like refined perception, mind control, and mental force projection. Operating with significant autonomy, Tregonsee specialized in intelligence gathering and covert operations against the Boskonian hierarchy.

During the Boskone conflict, Tregonsee participated in Earth's defense against planetary attacks and contributed to developing the "sunbeam" superweapon. Tregonsee later executed a critical espionage mission by infiltrating the Boskonian communications network disguised as a zwilnik, tracing enemy infrastructure to its core systems. This intelligence directly enabled the Galactic Patrol's invasion of the Second Galaxy and the assault on the Boskonian stronghold at Klovia.

Following Boskone's defeat, Tregonsee became Vice-Coordinator of the Second Galaxy under Kinnison, aiding in integrating conquered Boskonian territories into Civilization. Tregonsee's Rigellian nature and Second Stage Lensman conditioning placed them within the Arisian breeding program designed to produce beings capable of countering threats like the Eddorians.