User blog comment:OneofthePendragon94/Does someone know what happened to Morgana's mother Vivienne?/@comment-4892425-20130101180129

This was another missed opportunity by the writers and producers when they sprung that plot twist that Morgana is Uther's illegitimate daughter. They didn't flesh out the circumstances of Uther's and Vivianne's affair. (That throwaway explanation that she was lonely while Goloris was away comes off as lazy writing.)  Why was she lonely? Did Goloris neglect her for some time? Was Uther looking elsewhere for comfort because Ygraine failed to produce an heir through natural means? During that time it was no big deal that a king took another man's wife as his mistress, and the cuckolded husband was suppose to sheild his eyes and endure.

Here's another possibility:  Uther and Vivianne had something going on before Ygraine, with Vivianne hoping to be Camelot's next queen. Vivianne struck out and settled for Goloris. Ygraine's infertility caused a wedge in the royal marriage and Vivienne saw this as a chance to get back into Uther's bed. Her pregnancy with Morgana could have been intentional, showing that Vivianne can give Uther heirs while Ygraine cannot. This way Uther sets Ygraine aside and claims Vivianne and Morgana, thus living a life in the palace. If Uther didn't dump Ygraine Vivianne could still settle for being maitresse en titre, the king's official mistress, a position that can be just as powerful as the queen consort. But it didn't work out that way; Goloris probably figured out Morgana wasn't his child, but the parties involved decided to keep quiet so scandal doesn't bring down the royal house as well as the house of Goloris. Uther may still have been paranoid that Goloris may want revenge for betrayal of this friendship, and that's why Uther didnt' send reinforcements to Goloris went he was attacked.

As for Vivianne, she could have been put to death to prevent her from spilling about the affair;  or Uther found out she was a sorceress and that would have put his throne in jeopardy if it got out Uther, the father of the Great Purge, has lain with a woman that wielded magic.

This would explain Morgana's bad decisions, but it would not have absolved her from them.