The Age of the Seeker, alternately called the Night of the Seeker, is a period of non-time between the major ages within the Batsi calendar. It takes place during one night, during which any number of years may pass.
The Oolbat dies in the evening. The Oolbat is born in the morning. - Excerpt from Batsi Rite of Passing
It is traditionally held that the Oolbat, however old they may get during a given lifetime, will always die in the evening. Because of the Batsi understanding of time, this is impossible to verify, because the moment the Oolbat dies and a Seeker is selected, the Night of the Seeker begins - it is therefore always evening when the Oolbat dies, regardless of what time it may actually be. Similarly, the Oolbat is believed to always be born in the morning, but because the first 'day' of the Batsi calendar for a given age begins at the Oolbat's birth, it would necessarily always be morning, regardless of what actual time it is.
Either way, this period is not considered a true age in the same manner as the Oolbat ages, because reality is believed to be completely under the thrall of Illusion. As such, there is no access to the True World during this period, and true time doesn't pass. The whole concept is somewhat apocalyptic, as the very fate of reality hangs in the balance as the Seeker endures the full strength of Illusion. Failure to find the Oolbat at the moment of birth is believed to doom the world to eternal separation from the True World.
The night is dangerous, the world unprotected, souls susceptible to the machinations of Illusion and its servants. Everyone except the Seeker hides in their homes or the temple at Refuge, burning special incense and candles to keep the night at bay, and focus their minds on calling for the Oolbat to help guide their soul to their new body.