gshin rje - Yama

The big scary monster hogging the Wheel of Life is gshin rje, Yama in Sanskrit, or Lord of Death as it's usually translated. gshin is death, and rje is a honorific, such as Lord. It's good to learn rje, you see this in titles, such as in Je Tsongkhapa.

Yama belongs to a class of beings called Maras, or bdud in Tibetan. Externally they are represented by demonic influences trying to cause harm, but internally they are really all kinds of mental afflictions triggering problems.

In the Wheel of Life gshin rje represents the grasp of karma and mental afflictions forcing everyone to continue inside the samsaric, suffering existence.