The Lot of Eros, kleros erotos, is the lot of Venus in the Hermetic set, and it is calculated from the Lot of Spirit rather than from the Ascendant alone, which places it firmly on the volitional side of the scheme. Paulus Alexandrinus gives it for desire and for what a person wishes for, and Vettius Valens connects it with friendship, appetite and the objects to which the will inclines. It is important not to read it as a modern romantic significator: the Greek eros covers wanting in general, including ambition and appetite, and the Hellenistic authors use the lot for what a person is drawn toward rather than for love affairs specifically. Its pairing with Necessity, the lot of Mercury built on Fortune, sets desire against constraint, which is the axis the two are meant to be read on.
The day formula is Ascendant plus Venus minus Spirit; by night the terms reverse, Ascendant plus Spirit minus Venus. Ancient sources are not unanimous even on this much: the Hermetic formula transmitted through Paulus Alexandrinus and Olympiodorus builds Eros from Spirit as given here, while Vettius Valens and Firmicus Maternus in places preserve an older tradition built directly from the two luminary lots, Fortune and Spirit together, rather than from Spirit and Venus. Modern practitioners of revived Hellenistic astrology generally follow the Paulus formula given above, but the variation is well attested in the surviving texts, and it is a caution against assuming any single ancient formula for a lot was used uniformly across all authors and periods.