In the novel Edit
The Aunts are a class of women assigned to indoctrinate Handmaids with the beliefs of the new society and make them accept their fates. Aunt Lydia works at the Red Center, the re‑education school where Offred and other women go for instruction before becoming Handmaids.
Although she appears only in Offred’s flashbacks, Aunt Lydia and her instructions haunt Offred in her daily life. Aunt Lydia’s slogans and maxims drum the ideology of the new society into heads of the women, until even those like Offred, women who do not truly believe in the ideology, hear Gilead’s words echoing in their heads.
In the Hulu series Edit
In the beginning, she teaches the fertile women, including Emily, June, Moira, Alma, and Janine, about their new roles as handmaids. She then congratulates the women for their fertility, but when Janine scoffed at the idea of bearing children for the barren couples, Aunt Lydia shocks her with a cattle prod and later removes her right eye as punishment.
June is taken back to the Red Center from an attempt to escape. Aunt Lydia has June tied down whilst Aunt Elizabeth whippes the soles of her feet. .
Aunt Lydia knells to call the Handmaids together for a Salvaging, where she announces that they are here to execute a man who was convicted for raping a pregnant Handmaid, resulting in the baby’s death.
Offred is interrogated by an Eye and Aunt Lydia about Ofglen. She answers as honestly as possible whilst omitting the fact that Ofglen is a member of a rebel network. They then suggest that Ofglen may have tried to "touch" Offred, which she denies. When Offred admits that she knew Ofglen was a 'Gender Traitor', they ask why she didn't report the conversation. Offred replies that Ofglen was her friend. Aunt Lydia tells her that Ofglen was a "beast" and "abomination against God", angering Offred. When Lydia tells her to "remember her Scripture", Offred defiantly quotes another Scripture passage: "And blessed are those who suffer for the cause of righteousness, for theirs is the kingdom of heaven". Infuriated, Lydia tasers Offred and begins beating her, but is stopped by Serena, who declares she's pregnant.
All of the handmaidens are called to come together to stone someone who endangered a child. To their surprise, that someone is Janine. The handmaids hesitate and Ofglen #2 is brutally beaten by a guard when she breaks rank and voices her angry refusal. The other women, beginning with Offred, drop their stones, each saying "I'm sorry, Aunt Lydia" (a phrase they were taught early in their indoctrination). The guards are ready to kill them all, but Aunt Lydia frantically tells them that the handmaids are her responsibility. Aunt Lydia promises that they will all be punished and sends them home.