At some point in the past, Taal had been settled by the Taubat, one of the indigenous species in the Tabula Rasa.
In 2292, when the Orsa system, along with many others, were pulled into real space as a result of Project Shiva, the Klingon Empire chose Taal as the site of its first colony in the region due to its immense dilithium reserves. Soon after the colony was founded, the local Taubat attacked it in an attempt to drive the Klingons offworld. Unfortunately for the Taubat, their technology was primitive in comparison to the Klingons, and so their forces were quickly crushed, their settlements on the planet destroyed, and their temples looted.
The actions of the Taubat on Taal were later disavowed by their government; they claimed that the transition from the pocket universe of the Tabula Rasa into real space had maddened the population of Taal and turned them violent. The Klingon High Council accepted this explanation, with reservation.
In addition to the Taubat, an ancient fortress that was later determined to belong to the Hubrin was discovered on Taal during the initial Klingon occupation of the planet. (TOS video game: New Worlds)