The Caves of Donn come right before the Caves of Middai and the Caves of Eivnieng.
Tabula Rasa's Caves of Donn is an early instance which will provide players the unusual opportunity to oust the Bane from a friendly held position. NCsoft has been kind enough to provide a detailed briefing explaining exactly what is going on in the Caves of Donn, and the expectations of your squad.
In the central hills of the Concorida Wilderness rests a place of immense power and significance to the Forean natives. The Caves of Donn is home to a considerable number of Eloh artifacts which are of great interest to Bane forces. Your squads mission is to infiltrate the caves, neutralize any threat to the artifacts security, and assist the Foreans in defending against Bane incursions at all costs. NCsoft has provided a complete video briefing of this important assignment so watch carefully.
Go watch it at Ten Ton Hammer's TR site.