Later in the 2260s, Vanadala invited the Federation to sign a treaty to obtain her planet's korium, and made preparations for the USS Enterprise's arrival. When a ship hailed them, it was assumed to be the Enterprise and they were invited down. Instead, Klingon troops materialized, seized control of the palace, and began to steal the korium. Commander Kalor imprisoned Vanadala to prevent the population from revolting.
Vanadala was forced to warn away the Enterprise, giving them an ultimatum to depart within two hours. To reinforce her demand, the Enterprise was shot at by a planet-based phaser. Because Vega III was a peaceful planet without such weaponry, Kirk suspected something was wrong. He beamed down with a landing party, but Kalor recognized Spock and they were imprisoned with her. Before they could be killed by a firing squad, Montgomery Scott beamed her up, along with Kalor and the landing party. With Kalor in the brig and Vanadala freed, she was certain Kalor's troops could be handled. She signed a formal treaty for the korium before the Enterprise departed. (TOS novella: The Prisoner of Vega)