Cyrus Gold was a friend and henchman of season 2 villain Sebastian Blood. He managed to survive being injected with Mirakuru, and became an even more dangerous opponent than Blood himself, one capable of physically matching Oliver. Although Gold is seemingly killed when a mixture of chemicals are spilled over his face, there is a chance he could return as someone else: Solomon Grundy. Thats who his character becomes in the comics, a zombie who possesses superhuman strength and speed and is near-indestructible. Introducing a zombie character would be a big stretch for the more-realistic Arrow, but they could find a way to introduce him and his character traits without perhaps referencing that fact (or they could decide to fully-embrace a more supernatural world). Theres also a nod to Grundy in the show, as the poem is found in Golds apartment, and Oliver quotes a couple of lines from it: Died on Saturday, buried on Sunday. Solomon Grundy, born on Monday (or Wednesday, as thats when Arrow airs)?