Long story short, hes a foe of Phantom Stranger. The dog (his master, named Non), is the Presence's arch nemesis. Sin-Eater is a high end demon. I think this would be interesting.
GAL
Galan007|Quantum Observer|
Sin-Eater was implied to be Phantom Stranger's equal/opposite... In the same arc where PS was shown to be on par with Spectre, and a battle between them would have destroyed all creation.