A mindscape was a force power that generated an environment within one's mind, used by powerful force-sensitives to haunt and corrupt another's mind, such as when the soul of Tenebrae infected the Outlander after his own demise.
Some time before 3627 BBY, Tenebrae again infected others, locking Jedi Master Satele Shan within her own mind and feeding off it. In 3626 BBY, a task force led by the Eternal Alliance's Commander—formerly known as the Outlander—were able to enter Shan's mind, release her, and kill Tenebrae for good.