Bhagavad Gita, Chapter 8, Verse 9-10

The Omniscient, the Ancient, the Overruler, minuter than an atom, the Sustainer of all, of form inconceivable, self-luminous like the sun, and beyond the darkness of Maya - he who meditates on Him thus, at the time of death, full of devotion, with the mind unmoving, and also by the power of Yoga, fixing the whole Prâna betwixt the eyebrows, he goes to that Supreme, Resplendent Purusha.

A real list of qualities is offered here, not just a vague sense of greatness, and it ties straight into something practical: an actual method for that final, focused moment.

Krishna describes his own nature in specific, concrete terms, ancient, all-knowing, subtle, radiant, then returns to something usable. A real, specific practice, steady mind, focused attention, sustained devotion, is offered as the way that description actually becomes attainable at the moment it matters most.