This is one of those times I regret my six-episode minimum rule because I realized after the first episode what I was in for. King's Raid is about the worst kind of anime to try and review because there isn't a whole lot of negative to say about it. There also isn't anything good to say about it. Demons invade, a hero who is secretly descended from a king rises to try and fight, the light goddess that created the magical sword may or may not be evil. That summarizes pretty much everything you need to know about these first six episodes.
I finished watching them the day before I started writing this, and I can't for the life of me remember the name of a single character. None of them leave any kind of impression on you, and frankly, none of them have much beyond a one-note personality. Oh but the main character likes to eat cooked bugs, so I guess that's a personality now. All you need to know is he wants strength to protect people and that is as far as his character goes. You can probably construct a very accurate version of him in your head from just that. It's nothing but generic fantasy tropes here.
Tropes, in the end, don't work if you don't at least make your characters likable. The most generic of ideas can work as long as you can at least see yourself rooting for the guy, but there just isn't anything to any of these characters six episodes in. Doesn't matter which character, pick one and this statement applies. Later episodes may change this, but six episodes is far too long to go without giving you something to work with.
The fights are pretty underwhelming as well, and half the time feel like they are over before they begin. There isn't a whole lot of variety in demons so far either, which is fine if you can keep the fights engaging on something more than a purely visual level. Goblin Slayer did this fantastic with the majority of the fights just being against goblins, but here you see nothing interesting or intriguing happen.
The animation is pretty solid, but it's in service of some pretty uninspired art design. I'll admit the thorn demon that shows up looking pretty neat, but that is one thing that stands out. Nothing looks bad by any stretch, but even the main cast I struggle to remember what they look like beyond the most superficial of traits (The sorceress is a big boobed redhead ((Okay, I looked it up to see if I remembered right and it's pink hair, my bad))). Seriously, I watched this show yesterday, and it leaves this little of an impression.
I don't know what else to say here, barely anything that isn't easily predictable in a plot that this happens. Nothing about the show stands out, and if it weren't for the fact I am keeping a list ready for the end of the year top ten there is a good chance this wouldn't make it just because I will be shocked if I remember having watched it in a month.