Is Gideon talking about Marika or Radagon?
If I’m not mistaken there are only 3 confirmed people who know Radagon is Marika. Goldmask, Coryn, and us. I kinda wanna throw miquella in there as well since his relationship to St. Trina is the same as them so it could be possible that he put the puzzle pieces together but either way this line has NEVER made sense to me as the guidance of grace clearly wants someone to stop Radagon and Messmer himself believes that it’s Marika whose guiding us. I feel like this line only makes sense if he doesn’t know especially because we don’t get the option to tell Gideon(something I tried to do immediately in my 100% playthrough) and his armour does kinda make a point that Gideon had to accept that knowledge was unending. I also think this idea that “everyone should suffer” also fits Radagon’s mental state by the time we fight him.