I don't know how I missed it earlier, but upon re-reading the chapter I noticed that Lancelot has a bunch of arrows around his armband. This means that instead of creating arrows with his magic, he's actually just using the physical arrows he carries around with him.
This is actually really confusing to me, because I don't understand how he manages to shoot real arrows like this. Is he transforming into his human form, shooting the arrows with his bow and then transforming back? Is he pulling them out of his tail like with the map earlier and then accurately throwing them at his enemies' weak points? Either way he would have to be absurdly fast in order for nobody to notice him do that. In chapter 11, Sin was standing right next to Donny, Percival, Nasiens and half a dozen fairies when an arrow hit Talisker's doll, but none saw him shoot it. Same thing in this chapter when Elgin was hit by multiple carefully aimed arrows from the front while Sin was standing behind him. Could he really be moving so fast that nobody can even see his attacks?
Another option would be that the fox is actually just an illusion or something along those lines. That would explain why its body distorted when hit by those wind sickles in this chapter, but it would beg the question how the fox can interact with physical objects and even people. Perhaps it could be some sort of a magical construct, like a familiar? When Sin was standing next to Percy, Donny and Nasiens, the real Lancelot could hide in the bushes and snipe the doll without anyone noticing. When Sin was dodging the Talismans' attacks, the real Lancelot could shoot them while they're distracted, although he would have had to somehow get inside the perfect cube before it was activated and then remain hidden until the fighting started. There are some holes in this idea, but I kinda like it because it would mean that Sin the Fox could remain active as the mascot of the series even after the Lancelot reveal, since they would technically be separate characters.
Also, I wonder what Lancelot meant when he said he would not be able to tag along with the group anymore. The argument Sin had with Anne at the start of the arc had him question whether he's really part of their group, so he might just be thinking that Percy and co. won't accept him anymore now that he's revealed his true self. Alternatively there could be an actual reason for it, like someone being able to sense his location now that he's revealed his identity. Whatever the case, I'm hoping that Percy will be able to convince him to stay, because it would be a huge waste for Lancelot to just leave immediately after his identity was finally revealed.
It's hard to say what his magic does, but I like the idea of it being similar to Snatch. Something that's straightforward on the surface but that has more abstract and situational applications as well. Lancelot is the grandson of the Fairy Tree and the son of one of the strongest humans in history, so he doesn't really need to have a super special magic like Percival. Not to mention he's also got access to fairy abilities and maybe even some kind of remnants of the Fountain of Youth.
Yeah I think he's definitely getting a spear at some point. Nakaba portrayed Lancelot with a spear in Rising Impact and also in the one-shot, so he clearly associates Lancelot with that weapon. The spear he made out of a branch as a kid might actually be a reference to a story where Lancelot used a random tree branch to defeat an armed knight. I wonder if Lancelot could end up becoming a sort of weapon master who can use a bunch of different weapons equally well. Or maybe his spear could shapeshift into different forms just like his body, although that might overlap with King's spear a little too much. In the legends, the Lady of the Lake gives Lancelot a bunch of magical items including a couple of weapons. That idea could easily be twisted into some sort of a shapeshifting Swiss Army knife of Chaos.
