- Appearances: Camber the Heretic, The Harrowing of Gwynedd, King Javan's Year
Tavis O'Neill is born in 879, during the Festillic Interregnum and reign of Festil III. He receives training as Healer from both the Gabrielites and the Varnarites. His early Varnarite training left him permanently scared, injured psychically and physically--training injuries were quite common among Varnarite training. As a result he missed some key lessons which were later partially corrected by the Gabrielites. By 917, he is serving as the court-appointed personal Healer and tutor to Prince Javan Haldane, and assigned to the royal nursery to assist all three young princes. Tavis also acts as court Healer for others when others are not available. He quickly forms a close bond with the Javan, who needs his services regularly, suffering from a clubbed foot. Those close to Cinhil and the Regents after Cinhil's death worry about their rather codependent relationship. Javan is likely to be king one day, and they view Tavis as trying to shield and coddle him from the harsh realities of life. Javan in fact throws tantrums and refuses to eat when Tavis is not there.
Tavis was drugged by Rhys Thuryn in January of 917, in order to keep him out of the way while the three princes Haldane Potential was set. After the death of King Cinhil Haldane, Tavis is one of the few Deryni who is not forced out of the court, mostly because of his close friendship with Javan. Javan protects him from being imprisoned or killed.
In May of 917, Tavis is physically and magically attacked by a group of Deryni, his shields being brutally forced down as they beat him and they cut off his left hand as punishment for assisting the human-controlled court. During the course of his recovery, Tavis discovers that Javan is beginning to exhibit the early stages of the Haldane potential, and the two become determined to discover the source of Javan's fledgling powers. Tavis also uses Javan and his newfound abilities to help heal his physical wounds, further cementing their rather co-dependent relationship. Rhys and the other Healers make note that Tavis may be mentally and psychically unstable, a profound sense of bitterness and upset permeating him after the attack. They even contemplate ways to block his powers until he can be adequately assessed, but decide even that is too dangerous to attempt. Tavis is profoundly bitter that his own people did this to him. Healer's and healer's hands are considered sacred and wants to find those responsible.
Tavis reluctantly assists the Regents in interrogating Deryni, drugging and harming them, but refusing to violate his Healer's Oath and kill. Due to his close relationship with Javan, he is only barely gets away with it before they turn on him.
On December 24th 917, Tavis and Javan capture Rhys and drug him to force his cooperation, enabling Tavis to force a probe into Rhys' mind to find out what happened on that day of January 917. Not only does Tavis uncover additional information about Javan's powers, but he also discovers that he shares Rhys' ability to block Deryni powers. Shortly thereafter, as the Regents of King Alroy unleash a violent wave of anti-Deryni persecutions. When Javan can no longer protect Tavis, he is finally forced to leave Javan and the palace and join with the outlawed Deryni rebels.
Tavis is inducted into the Camberian Council in 918, and he spends much of the next several years working closely with Revan and the Council's covert baptizer cult. In an effort to protect Deryni from the persecutions, Tavis covertly blocks their powers while Revan baptizes them, making the process appear to be a divine miracle. Tavis lets the very real bitterness he feels at being attacked by his own people be used as a cover for his supposed conversion by the baptizer cult. Tavis is briefly reunited with Javan prior to Javan's coronation in 921, and Tavis plays a minor role in fully activating Javan's powers. The following year, the former Regents launch an assault against both Javan and the baptizer cult, and Tavis, Javan, and Revan are all slain in the massacre. Tavis is brutally torn apart by the angry baptizer cult after they realize he still has his powers, after he shoots lightning trying to save a child. Tavis dies in 922 at the age of 43.