I get the legend stuff. Just the whole "party" thing and the "wake up after four hours sleep" sequence in episode 24. Continuity seems to be off - along with how they just completely dropped the "E" sign on his chest, and the significance of his dad stabbing him.
Lucile is apparently the Weaver of all Equations (but shouldn't that exist in the Dark Hero then?).
Ferris' brother made Sion into the Dark Hero... who needed to 'eat' the Satan to be powerful.
As for eating Ryner.. was that the reason why Sion wanted to kill him? I never quite understood how killing Ryner was going to save him from walking through eternal darkness, unless it's like "kill him or eat him".