death is personified as Yama, the Controller, for it is he who administers the central law of the phenomenal world: that all of nature is in continuous change, and therefore whatever comes into existence… must someday pass away.
Easwaran establishes Yama as the personification of the universal law of impermanence—not an external deity but an interior force governing all phenomenal existence.
, Essence of the Upanishads: A Key to Indian Spiritualitythesis