Mother of Cúchulainn, daughter of Cathbad the druid, lover of Lug Lámfhota, usual sister of Findchóem, and sometime sister or daughter of Conchobar mac Nessa. The most familiar version of her conception of Cúchulainn is that, while grieving the loss of a foster-son, she drinks some water with which a tiny creature passes into her mouth; the creature may be Lug, or she may merely have dreamed of Lug. Before the child can be delivered, she is married to Sualtam mac Róich. In a second version, Deichtine disappears with fifty maidens from the court of Conchobar mac Nessa. After a lapse of three years a flock of birds settles on the fields of Emain Macha and lays waste the crops. When Conchobar and his retainers seek to drive off the birds, the birds lead them on to the magic mound of Angus Óg on the Boyne. At night the men come upon a splendid palace, where a noble youth is accompanied by fifty maidens. The maidens include Deichtine, and the noble youth is Lug Lámfhota. On hearing the news, Conchobar asks to see Deichtine, but she sends him instead her newborn son Cúchulainn. In a third version Conchobar, as either Deichtine's father or brother, commits incest with her to father Cúchulainn.
The character of Dectora in W. B. Yeats's The Shadowy Waters (1900) appears to be based in part on Deichtine.