I finally light one of the four Primal Bonfires after clearing out Sinner’s Rise of The Lost Sinner.

Three things: 1) Sellsword Luet doesn’t really DO anything and should not be summoned, 2) Lucatiel’s AI likes to just walk up to the Lost Sinner and stare at it for a while, and 3) the Lost Sinner appears resistant to fists, so that was unfortunate.