Trecena 18 runs from 1 Ehecatl through 13 Ocelotl, jaguar, its span carrying wind, house, lizard, serpent, death, deer, rabbit, water, dog, monkey and grass before closing on the very sign that opened Trecena 2 near the count's beginning, now carrying the number thirteen rather than one, a second instance of the day sign vocabulary folding back on itself as the tonalpohualli approaches its final two trecenas. This trecena sits within the count's last quarter, and the changeable, unsettled reading it carries under Chantico's patronage continues a mixed run of favourable and difficult weeks that alternate through the tonalpohualli's later stretch without settling into a single consistent trend as the count moves toward its close.
The house sign crossed early in this trecena's span carries, elsewhere in the count, its own reading of enclosure and caution under Itzpapalotl's patronage at Trecena 15, while the jaguar sign that closes this trecena carries the hard augury Trecena 2 itself opened on, so a diviner reading this week's full thirteen days would have moved through echoes of two of the count's more demanding trecenas within a single unsettled week. The recurrence of an earlier trecena's jaguar close beside this week's own house sign echo gave the tonalpouhque a ready comparison to draw for a client uncertain how seriously to weigh an unsettled reading, pointing back to the fuller augury already on record for the sign's first appearance at the count's opening third.