The Mirror of Remembrance was the name, given by the Mind Walkers, to the surface of the Lake of Apparitions. This lake was beyond shadows, a realm of the Force to which Force-sensitives traveled after separating their minds from their bodies. In the Mirror one could view and talk to spirits of beings who had died.
In 43.5 ABY, Jedi Grand Master Luke Skywalker and his son, Jedi Knight Ben Skywalker, embarked on a quest to find out why Jedi Knight-turned-Sith Lord Darth Caedus had fallen to the dark side of the Force. Eventually, their journeys led them to seek out the Mind Walkers, who they found at Sinkhole Station in the Maw. When Luke and Ben went beyond shadows with Mind Walkers Seek Ryontarr, Feryl, and Rhondi Tremaine, they crossed the Lake of Apparitions in order to find a strange being to find out what she wanted, as she had been forcing Ryontarr and Feryl to stall Luke, and prevent him from returning to his body. As they began to cross the lake, they saw in the Mirror of Remembrance the spirits of Anakin Solo, Mara Jade Skywalker, and Caedus; and spoke with all of them.