Summary of our selection procedure to reveal Specter in Gaia DR3 data. Top: reflex-corrected proper motions in our transformed great circle coordinates, after applying an isochrone filter to select stars at ≈12.5 kpc. Our proper motion selection is shown with a red ellipse, and is centered on the mean proper motion of the H3 members. Middle: CMD of stars that lie in the proper motion ellipse shown in the top panel, without any CMD filtering applied. We overlay a fiducial 13 Gyr MIST isochrone with [Fe/H] = −1.8 and [α/Fe] = +0.3. Bottom: spatial density of stars that pass both the PM and CMD filters, smoothed with a 1.°5 Gaussian kernel. We overlay the spectroscopic members and their predicted orbit.