The way SK has been portrayed in episode 359 was very suspicious. Why did Miura decide to depict him that way? Did he do that just to create a dramatic build-up, or is there something more behind it? I mean, even the preview text on the left that we can find on the last page of episode 359 implies this might be the case.
So far, SK has been helping Guts indeed and gave him information and also a choice between saving his loved ones and pursuing revenge (which can be considered a green flag; but beware of the illusion of choice). He warned Guts on the beach of the dangers of the Berserker Armor and told him about the possibility to restore Casca’s mind.
“To protect or to contend? You will continue to query your own soul. It’s your fate as man who stands in the interstice”
But remember that even Flora at some point questioned his intentions. In volume 24, It was presumably Skull Knight who told Flora to help out the Black Swordsman. In this chapter, she was even surprised that he would even ask her for help (this is fascinating, given that Guts isn’t the type to ask for help either, which indicates Skull Knight in his human form must have been a stubborn, solitary type). But, in the same bit, her words signal to us his actions and help is to be taken with a grain of salt:
“Is it for someone’s sake? Perhaps pity for a fellow sufferer? Or… are you just using him?”
Now again at the end of episode 359 we are reminded that his intentions are to be questioned: “The knight appears as the recurring nightmare widens the gulf the two… what are his intentions?“
Episode 359 and 360 stand out in many ways in regards to Skull Knight. So far he only has appeared at night time before Guts and this is the only time we see him in daylight together with the Black Swordsman. However, just because he is seen in bright daylight doesn’t mean he’s still Guts’ ally, speaking from a writer’s point of view. No, the opposite might be the case, much like the reunion of Guts and Casca in chapter 355 wasn’t exactly a happy one despite of the setting.
We can take a look at previous occasions of Skull Knight appearing before Guts, to get a feeling for this. He was always a mysterious character, but was not depicted as suspicious.
 When Guts camps out in the wilderness after he left the Hawks, our bone dad is depicted as intimidating shadow towering over Guts, presumably because he was a threat. I believe he had the intention to kill Guts to prevent the Eclipse. If it’s true that Skull Knight does not hesitate to even kill allies when given the chance, e.g. to counter the God Hand’s plans, his intentions are to be questioned indeed.
 Skull Knight appears when Guts and his companions settled in a cottage close to the beach. Here his appearance and the way he is depicted the seems mystical but still neutral enough.
 When appearing at Flora’s mansion, he is only depicted as a shadow. Vague, but it is still obvious enough it is Skull Knight. Consider for a moment this occasion is in bright day light, yet he is not stepping forward like in Episode 360. He would only show himself when defending Flora from the apostles later.
 Now what do we have here? Partially hidden face behind the branches, hiding from afar? He looks like some mischievous thief who is up to no good, peeking from behind a tree… I mean, come on….. Even though SK was always a character clouded in secrecy and mystery, this is a new level of fishy in my opinion.
 The Knight then appears before Guts when he was just wondering what the hell he is about to do now. How very convenient! A solution has just arrived! You know how salesmen or adverts try to sell you things by first describing a very relatable problem, and then offer you an easy solution (their product) in order to make profit? This is here is almost the same thing: remember, Skull Knight was the one who played with Guts’s hope to make him take this very direction in the first place.
To make Guts go after the God Hand, just run a plow between him and Casca (i.e. by restoring her mind). He’s gonna fall for the “restore Casca’s mind”-bait because of how deeply he cares for her. Then catch Guts in a “I told you”-moment and offer him your solution, which now appears like the “better” one. Guts’ behavior is predictable and Skull Knight could have used that in his favor. If you want to tell me only the God Hand is good at calculation and manipulation, you’re terribly wrong.
What is also very dangerous is the fact that Guts is all alone with Skull Knight in Episode 360, without Puck or Schierke present. In the past, the worst things happened when Puck or Schierke were absent, e.g. Guts almost dying from spectres (without Puck) in chapter 118, Guts forcing himself on Casca (without Puck) in chapter 190, Guts almost going after his companions as the Berserker when Schierke was away in chapter 316. There are more occasions like these, but let’s leave it at that.
I think there are enough reasons to be suspicious of Skull Knight. Even if Skull Knight again foretold him to either protect or to contend like last time, offering someone two options is not really a choice, in my opinion (create your own choices, dammit). Fortunately Guts has always been snarky and suspicious towards bone dad, so he might not fall for it and find his own way instead.
Given everything I pointed out I am seriously wondering whether we are in for another episode of “trusted father-figure betrays Guts”. If not, it’s possibly Miura just messing with his audience. But, it’s also smart of him, because like this it’s harder to predict what’s coming next to keep the story interesting. Skull Knight being a truthful and reliable ally to Guts is still possible because of the ambiguity of Miura’s writing. Either way I am looking forward how this plays out!