Dark Emperor
Dweller of the Lotus Moon
I sort of just realized this, but in volume 38, Erica makes some off-handed remark referring to Guts and the Dragonslayer to both Luca and Daiba, but none of them can remember him. I found that to be pretty odd as they both had very prominent experiences with him that they shouldn't just forget him, especially Daiba who had to actually fight Guts. Maybe there's some serious mindfucking going on besides the souls of the dead schtick Griffith has going on.