Starfield Backdrop Only
Architecture BP_PathFollower (on the scene) – Finds nearest spline key computes forward/tangentproduces push impulses → interpolates Player and Rock together.
BP_SysyphusChar (Player) – Receives AddWorldOffset / SetWorldLocation(FInterpTo) style moves; maintains spacing/alignment with the Rock.
What the BP does

See details →
Pseudocode
worldPos = Actor.GetWorldLocation()

key      = Spline.FindInputKeyClosestToWorldLocation(worldPos)
dirAtKey = Spline.GetDirectionAtSplineInputKey(key, WorldSpace)
dirNear  = Spline.FindDirectionClosestToWorldLocation(worldPos, WorldSpace)

optional: also pull a little toward the spline centerline
closestPos = Spline.FindLocationClosestToWorldLocation(worldPos, WorldSpace)
toCenter   = Normalize(closestPos - worldPos)

blend and normalize (weights are tunable)
dir = Normalize( 0.6 * dirAtKey + 0.4 * dirNear + 0.0 * toCenter )

fallback if degenerate
if Length(dir) < 1e-4:
   dir = dirNear    # or dirAtKey

rot = MakeRotFromX(dir)  # or dir.ToRotation()