Lachlan is an explorer made of amber crystal that the party encountered in the Black Riage along the border of Thaemore. She journeyed with the party to Osmus before parting ways to further study, and travel the Obelisk Network.
Lachlan has a history with Vlad, having known him when he was embedded in the Order of Truth as a (unbeknownst to them) false Aeon priest, using the alias 'Ikaris'. During their time adventuring, they became friends, and he provided her with the information that would eventually lead her to Osmus and the collected lore around the obelisks that is housed there.
She originally traveled with Manta Ray as both mount and pet, but gave him to Dili when she realized that Manta Ray would be unable to accompany her through the Obelisk Network.