The Animus researcher who becomes a playable character in Assassin's Creed Valhalla is Layla Hassan.
Layla is the modern-day protagonist of Valhalla. Using an Animus, she explores the genetic memories of Eivor, a Viking who settles in England during the ninth century. Layla's investigation connects Eivor's story to the series' continuing conflict between Assassins and Templars.
Players control Eivor for most of the historical campaign, but Layla's modern-day sections are directly playable. These segments advance the present-day plot and provide context for the visions, artifacts, and mysteries surrounding the Animus.
Rebecca Crane and Lucy Stillman are important modern-day characters from earlier games. Sofia Sartor is associated with Revelations, but none of them is Valhalla's central Animus researcher.