Looking at other people's theories, it could be either being ordered to reside there by the Emperor as penance for his failure to defeat Obi-Wan, or a deliberate choice to remind himself what happened, and continuing to fuel his anger.
Looking at other people's theories, it could be either being ordered to reside there by the Emperor as penance for his failure to defeat Obi-Wan, or a deliberate choice to remind himself what happened, and continuing to fuel his anger.