Kṛṣṇa describes the two ways by which yogis depart: the bright path — of fire, light, day, the waxing moon, the northward sun — treading which the knowers of Brahman go and do not return (8.24); and the dark path — of smoke, night, the waning moon, the southward sun — by which the meritorious go, attain the lunar light, and return again to be reborn (8.25). These are the “bright and dark paths of the world”, eternally set (8.26); by the one there is release, by the other, return. The imagery is old and symbolic — light for the direct, knowledge-led ascent that does not come back, smoke for the merit-led ascent that must.