Terla is an official of the pre-warp world visited in Time and Again, whose polaric energy plant Janeway and Paris reach one day before the explosion that wipes out the planet's population.
Terla appears in the first-season episode Time and Again. Janeway and Paris, thrown back a day in time by subspace fractures, find themselves among the inhabitants of a world that depends on dangerous polaric ion energy and is about to be destroyed by it.
Terla is the authority figure they run into as they poke around: he finds the two strangers suspicious, and Janeway has to improvise a story about coming from distant Kalto province to explain their odd behaviour.
His side of the argument is the official one, that polaric power is safe, set against the protesters led by Pe'Nar Makull who want the plants shut down. Neither side is the true cause of the disaster, which turns out to be Voyager's own rescue attempt, undone when Janeway seals the fracture.