Yugi's grandfather owns the card shop he and Yugi live in, and suffers from bouts of senility, frequently forgetting where he is and what is going on. He apparently lives in the basement of his own card shop and is often treated quite badly by Yugi. He frequently ponders his own death, calling the people in the obituary 'lucky bastards'. Solomon's body however, simply refuses to die. To date, Solomon has survived multiple assaults (Episodes 1, Abridged Movie), having his soul sucked from his body and placed in a coma-like state for an extended period (Episodes 2 to 19), extended periods of dehydration and exposure (referenced in Episode 20), constant animosity from his own grandson and assorted friends, and a harpoon injury from Mako Tsunami (Episode 33). Solomon has fought back on occasion though. After Yugi claims that "Santa" should go to hell for always giving him trading cards (when that's what Grandpa always gives him for Christmas), Solomon threatens Yugi that he'll kill him in his sleep, freaking out Yugi some. Solomon is also known to forget that Yugi is his grandson (Episode 62).
In the past Solomon seems to have been a highly experienced "Egyptologist", duelist, and general adventurer type. In Cr@psule Monsters 2, he's alive and well, exploring somewhere between Japan and India (and definitely not the scenery from Duelist Kingdom in season 1). It could be assumed that his bouts of memory loss, eccentricity, and general stupidity may be attributed to one too many head wounds, some sort of exotic disease, or an Egyptian curse.
Solomon has similarly colored eyes as Yugi, is short, and in Cr@psule Monsters 2, his hair seems to naturally spike up in an absurd fashion. In the second Christmas Special it is hinted that he is most likely Yugi's paternal grandfather.
Solomon seems to have a forbidden love with the Black Luster Soldier poster.