The Eternal King

I was thinking about the concept that some cultures have of death, that it is merely a passing of life and that the deceased retains all the rights and property they had in life.
So his children do not inherit and have to build their own wealth from scratch.

I thought how such a concept of death could fit into a fantasy universe.
A king who never dies and continues to rule (through his "loyal ministers"), without the possibility of being deposed, or assassinated.
With everyone under him forced into an eternity of stagnation, with no hope of change or improvement.
Whether said monarch is then actually still present in the world of the living is irrelevant.
Magic or simple political manipulation?
How to get rid of such a tyrant?

Visually, I was inspired by the relics of Catholic saints and the wonderful jewelry and jewels of the nomadic cultures of the Middle East.