The Battle of Basilisk occurred in the early stages of the Great Sith War.
On the world of Basilisk, the Mandalorians initiated their holy crusade targeting the Basiliskans. Despite receiving Republic reinforcements, the Basiliskans were overwhelmed and, in a final desperate act, poisoned their own planet to repel the invaders.
Although the Mandalorians left the planet, they successfully captured a significant number of Basiliskans. These creatures eventually became the Lagartoz War Dragons. Jedi Master Sidrona Diath perished during this battle. The Mandalorians subsequently relocated from Basilisk to the planet Kuar, where Mandalore the Indomitable later dueled the Jedi Ulic Qel-Droma.
According to The Essential Atlas, the invasion of Basilisk took place in 3997 BBY, during the Great Sith War; however, The Essential Guide to Warfare places it 20 years prior, in 4,017 BBY.
The in-game encyclopedia entry for Basilisk within the PC game Star Wars: Rebellion incorrectly claims that Sidrona Diath was killed by the Sith.