Hyleg
Hyleg is a chart point that, according to classical tradition, corresponds to life force. Candidates are determined in order: Sun in a daytime chart, Moon in a night chart, then Ascendant, Lot of Fortune, and the degree of the previous syzygy, i.e. the last New Moon or Full Moon before birth.
A candidate becomes a hylic if positioned in a suitable chart place and possesses essential dignities. Ptolemy described this procedure in Tetrabiblos, Bonatti detailed the conditions, and the calculation in the tool is based on them.