Alys is allegedly a bastard of the Strong family, although it’s not actually clear who sired her. The historian narrator in the source material, “Fire & Blood,” mentions some speculation that Alys is the daughter of Lyonel Strong, which would make her the half-sister of both Larys Strong (a.k.a. Clubfoot) and Ser Harwin Strong. There are some problems with this theory, however — mainly that Alys appears much younger than her supposed forty years, and that she’s heavily speculated to be a witch. 

Another theory from Mushroom, a dwarf jester on Rhaenyra’s side who is secretly recording all his thoughts on the Dance of Dragons, is that she’s “a malign enchantress who bathed in the blood of virgins to preserve her youth.” Mushroom also believes that Alys was far older than the other sources claim, believing Alys to have been “wet nurse to both [Larys and Harwin], perhaps even to their father a generation earlier.”

The book also gives attention to how all of Alys’ children had been stillborn, which spurred theories at the time that she’s “a witch who lay with demons, bringing forth dead children as payment for the knowledge they gave her.” The “Fire & Blood” narrator doesn’t give much credence to this theory, but Mushroom fans know that the dwarf’s testimonies always tend to have at least a shred of truth to them, at least as far as the “House of the Dragon” canon is concerned. From what we’ve seen of TV Alys so far, she definitely seems to be dabbling in witchcraft.