Void’s God Hand is mirroring Femto’s; both of them being the central target of revenge for Skull Knight/Guts, they both have a female member, there’s a duo with similar design aesthetic, and one guy who looks like an authoritative figure (Void for Femto, and that guy with a beard for Void). Since there’s been a theme of repeating cycles, I’d say the bearded guy is Void’s predecessor, as Void seemingly is for Femto.
The woman dying/fainting in Skull Knight’s grasp doesn’t look like Slan to me, though I know people have theorized before that the female figure on his horse’s chest armor was meant to be Slan. Honestly, the fairy aesthetic of the jewelry and her resemblance to Danann seems the more obvious connection, and I’d wait until we see how Slan looks in Moira’s current art style before coming into any conclusions. When in doubt on manga character appearances, though, I look at the hair, so unless this woman somehow becomes a God Hand despite being branded and changes her hairstyle, I don’t think she’s Slan.