I can't help but compare this series to Made in Abyss, and my honest advice would be to just watch that instead as it accomplishes what Magmell tries to do, but so much better.
Magmell is about a new continent that mysteriously appears with many new strange creatures and environments. The main characters are Inyo and Zero. Inyo is a "lacter" who can create objects at will, and an angler, someone who travels to Magmell often to rescue people who get into trouble. Zero is his assistant. Its premise sets it up to be an interesting adventure anime.
The problem comes with how bland and average it is. It really does feel like a bootleg version of Made in Abyss. It's not horrible and if you're looking for a short adventure series, it gets the job done. But its episodic nature prevents it from accomplishing so much more. The characters constantly jump between Magmell and their home each episode (save for the last few) to rescue someone and that's it. There's no sense of wonder or world building because the series never has time to create any.
If the series were longer, with the characters spending prolonged time in Magmell each mission, that could have really helped a lot. But without a solid narrative arc, or even a few medium sized ones, much of the series feels like filler besides the opening and ending episodes (which have an actual antagonist). The audience hardly learns anything about Magmell, which should be the whole point of the series. We also never learn anything about lacting. The villain comes out of nowhere and we know nothing about him except he's apparently a bad guy who does bad things. Another main character named Shuin is also constantly mentioned who everyone seems to know but the audience is never told where he is or why he left Inyo, his pupil
Rather than bland or average, it might be better to describe it as being an empty shell of something great and unique.
It's not all bad, though. For a shell, it's good! I opted to watch the series in English and the dub is solid. Erika Harlacker is one of my favorite new voice actors and her child-like voice for Zero is adorablly fitting. You also have heavy hitters like Keith Silverstein, Cristina Vee, and Jameison Price (*so* surprisingly playing the dastardly villain) making recurring appearances. The main theme is also pretty good as is the rest of the soundtrack (although the opening and ending tracks are lacking).
As it stands now, if we ever get more of this explaining lacting or or the characters spending more time in Magmell actually exploring stuff, I could bump this score up to a 6 or a 7. But for now, I would recommend you just watch Made in Abyss instead, which does much better with these same themes, in the same amount of episodes, and if you've seen it already, you can probably skip this.