The above about Abaddon/Apollyon/Abbaton is the most interesting thing I've ever read about the Sentry.
There are clues which led me to this conclusion.
First, Reynolds is a drug-addict and he was diagnosed as agoraphobic, paranoid schizophrenic, suffering from GAD (Generalized Anxiety Disorder) and from a premorbid schizotypal personality disorder.
In other words, he is self-destructive.
Then, newspapers referred to the Sentry as "the Golden Guardian" and the Sentry is also a bringer of light like Lucifer, one of the fallen angels. Abbaton was first appointed as a guardian on Earth. Everyone, including the angels, demons, and corporeal entities feared him.
Then, Abaddon is the leader of an army of giant scorpion-tailed locusts.
And, at the ending of the 'Siege' story, the Void looks like that :
Then, the Void has tried to explain to the Sentry what it/he/they is/are :
"So you're not a hero. You're me. You're a force. Lindy was right. You're part of something bigger than both of us. You are God. ... You want to do something? You want to have an impact? Allow me. I've done it before. And something good always came out of it in the long run. Yes, sure. It's a messy thing. It's God's way."
The Void also compared himself/itself to Galactus.
In other words, the Sentry/Void is Destruction incarnate (Abaddon in Hebrew or Apollyon in Greek).