mental body - Thubten Chodron

The body taken by arhats and pure-ground bodhisattvas caused by the base of latencies of ignorance and unpolluted karma.

The root of samsara
Continuing teaching from Chapter 7, explaining how different tenet systems describe what is the root of samsara and how the first link leads to actions.
Glossary: base of latencies of ignorance
Glossary: unpolluted karma
Verse 1: The realms of samsara
Why is it so hard to break free from the realms of cyclic existence? It's hard to eliminate its cause, the ignorance grasping at true existence.
Chapter 1: Verse 1
Explanation: there's no irreparable gap between who we are and the goal of Buddhahood. The mind is the nature of clear light and obscurations are adventitious.