Complex sentence: The Nrisimha mantra, with its four supplementary mantras, which are enunciated with the epithet "mantraraja" (king of hymns), has "Om" as the forerunner which is repeatedly emphasized throughout this Upanishad.
Split into simpler sentences: The Nrisimha Mantra, with its four supplementary mantras, is enunciated with the epithet "mantraraja" (king of hymns). It has "Om" as the foremost hymn which is repeatedly emphasized throughout this Upanishad.