The 27 nakṣatra-devatā mantras come primarily from the Taittirīya Brāhmaṇa 3.1.1 through 3.1.5 (the Nakṣatra-Sūkta), with additional verses from the Ṛg-Veda, Atharva-Veda, and standard pratiṣṭhā-texts. Each mantra invokes the devatā traditionally associated with that nakṣatra: the Aśvin twins for Aśvinī, Yama for Bharaṇī, Agni for Kṛttikā, Brahmā/Prajāpati for Rohiṇī, and so on through the 27.
Practical use: when the Moon transits a specific nakṣatra (which happens roughly every 24 hours), the tradition considers that nakṣatra's mantra particularly resonant for that day. /daily surfaces the mantra-of-the-day automatically based on the current Moon-position. /mantra gives you the full 27-mantra collection.
Classical recitation-counts use Vimśottarī-derived multiples: 9, 27, 54, 108, 216, 432, 1008. The pre-recitation invocation traditionally identifies the ṛṣi (seer who first received the mantra), chandas (meter), devatā (presiding deity), bīja (seed-syllable), śakti (energizing principle), and viniyoga (intended application).
Ethical framing — we present these mantras for what they are: classical-text fragments from the Vedic-Brāhmaṇa corpus with their original devatā-assignments. The practice of mantra-recitation is an attention-discipline. We make NO predictive claim that chanting will produce specific outcomes; we point to what the classical tradition preserves.