Trecena 10 opens on 1 Tecpatl, flint, under the patronage of Mictlantecuhtli, lord of the dead, with Tonatiuh the sun standing beside him in the codices, a pairing of the underworld and the sky's brightest body that marks the count's exact halfway trecena, the tenth of twenty. Sahagun ties the flint week to Huitzilopochtli, the Mexica's patron war god, and gives it a strong augury of courage and success in war and prosperity for those equal to its demands, a hard, bright week the readers judged favourable chiefly to the resolute, since flint itself, the sacrificial blade's own material, read as a sign rewarding those able to meet its severity rather than shrink from it.
Tecpatl is also one of the four year bearer signs, so this trecena's opening day could, in the separate 365 day solar count, name an entire fifty two year span of years bearing its number, giving the flint week additional significance beyond its own thirteen days whenever a year happened to fall on it. The pairing of the death lord with the sun in this trecena's patronage echoes the wider Mexica association of Huitzilopochtli himself with the sun's daily battle against darkness, fought and won anew each morning with the nourishment of sacrifice, a theology this trecena's hard, war favouring augury reflects directly.