Magic can be a tricky element to add to any series. The main problem with magic is that it is a powerful spice that can easily ruin a dish if it added without careful thought. The easy way to ruin the story is to just throw a ton of magic into a series without any careful measurement.
If you just dump MAGIC into a story it can easily unbalance it. There are entertaining stories to be told about what people do with nearly unlimited power but they have to be carefully constructed. If you just add such power to a normal story it can make everything feel arbitrary. When there is no structure to the magic in a series it can feel that obstacles are overcome and conflicts are resolved in a willy-nilly fashion or by deus ex machina. Challenges only exist until the story feels like they need to be removed. It can feel that progress is never earned since the characters can do anything whenever they need to since there are no real well-defined constraints on their powers. Also, characters can feel wildly unbalanced. They might seem untouchable demigods at some points and then flimsy humans then next minute with their exact power merely dictated by whim.
Even series that are fairly strong about balancing magic can fall into this trap. Read any nitpicky review of a Harry Potter story and it will be filled with comments about why did character X not use spell Y at point Z. While most of the time a healthy amount of suspension of disbelief inherent in the genre will smooth things over it is not that hard to spend that goodwill in a more sloppily written story.
The way to overcome this problem is to add restraints to the magic in a story. If magic has boundaries and limits then the more standard story progression can take place. But the problem is that this can also kill the power of magic in a story if it is too harshly applied. I love highly detailed and well-defined magic systems. The problem is these can easily take the magic out of magic for many readers. It can make magic feel like science with an occult paint job. A rigidly defined magic system can avoid the inconsistent feeling of magic but destroy the very essence of its appeal.
The other major way to limit magic is to set things in a low magic world where only a handful of people can use magic and therefore you keep it out of the hands of anyone but secondary characters. Lord of the Rings and Game of Thrones are prime examples of this. The major drawback is that it means you can’t have your protagonist be a magic user which can severely limit your options. Also, you still get Gandalf and the Eagles problems but they are at least contained to side characters.
But these are hardly the only ways of limiting magic for better storytelling. In fact, different solutions to this problem can be the seed for a story in of itself. Atelier of Witch Hat is a great example of this. In the world of the manga magic is the nearly limitless power but it is the witches who practice the craft who limit how it is used. All the constraints on magic are self-imposed by the practitioners. It combines several of the above methods into one which transforms the idea into its own device letting the manga tell a story around the concept.