When Vecna pursues Max in the middle of Stranger Things season 4, he takes things extremely personally. Vecna targets Max while preying on the town's most traumatised young adults, driving her into a terrifying spiral that prompts her to draught a number of private letters to her friends and family in case the demonic figure claims her life. In Stranger Things season 4, volume 1, only Max's letter to her deceased brother Billy is read. The rest of her emotional letters, however, have remained a mystery because the kids were able to keep Max alive, which has piqued the interest of viewers greatly.
Sink discusses what may be contained in the letter to Max's friend and ex-boyfriend Lucas in her interview with THR (Caleb McLaughlin). Sink has her own theories on what her Stranger Things character would have said to Lucas if she had known the end was close, though she isn't completely sure.