23 hours.

"Sheila" is a corruption/Omnarom hypercorrection of "Shiûl" which, in turn, is a transliteration of "Sheol" in Omnarom. This is basically an indo-brazilian cattle-shaped terminal that facilitates the sorting of souls in the local cluster, such souls being under the influence of an artificial reincarnation system. Zeranon entities are usually unable to survive outside the influence of this soul system (anywhere too far away from a Shiûlaska, "Sheol star"). Even if they do survive elsewhere, their dream body (the "soul") will necrotise, depriving them of their ability to reincarnate. Such zeranon cease to exist once they die.