I suppose it depends on what one means by 'power'. All of the standard mundane definitions still apply: there are still monarchs and warlords and whatnot, whose power derives from politics, money, or armies.
But yes, there's definitely also magic. Three flavors of it, in fact. And how powerful you are with each one comes with costs, trade-offs, and advantages.
Arcane Magic 
This is the stuff of wizards. Arcane magic is functionally the source code of the universe; anyone who knows it can manipulate reality.
Cost: Accessibility. In order to know arcane magic, you nearly always have to be taught. This is a huge investment of time, energy, and often actual money. This knowledge is extremely specialized, very difficult to learn, and some of the components for more exotic spells can be kings-ransom levels of expensive. Few small towns will have an arcane practitioner more powerful than a family witch or medicine man, who knows a few mild spells that have been handed down through generations. If you want the big, flashy, mountain-shattering, dragon-slaying magic, you're almost definitely going to have to go to a major city, and hope that you can get into a mage college, or at least find a wizard in need of an apprentice.
Advantages: High level arcane practitioners answer to almost no one, including some gods, and no one, shy of a more powerful mage, can take their power away from them. If you have the knowledge, the personal oomph (which varies from person to person), and access to the supplies you need, you basically don't have to take reality's crap. This means that powerful magi are highly sought-after by rulers and other wealthy individuals, and can be paid very well for their services.
Disadvantages: Besides the sunken costs (access to training, the years necessary to learn, the extreme difficulty, the expense), one of the disadvantages of being a powerful arcane practitioner is being considered a potential threat. The only real threats to a very powerful mage are other very powerful magic users, so the arcane community takes self-policing very seriously, and reacts with suspicion (at best) to mages who pursue frowned-upon magics. And very little can make you regret your decisions like a motivated archmage trying to protect other people from you.
Divine Magic 
This is magic granted by a deity to a worshipper. The worshipper doesn't necessarily understand how magic works, but they don't need to-- their deity does. All they need to do is press the button they've been given.
Cost: Spiritual devotion. Divine magic is limited to the devotees of a particular deity. If you aren't a worshipper of that particular deity, you won't have access to their magic. You're often limited to one deity, too-- they don't usually like to share.
Advantages: Accessibility is a big one. Almost every town has some sort of shrine to even a small local deity, and if there's a monetary cost at all to serving said deity, it pales in comparison to the fiscal costs of pursuing arcane magic. If you have a deity handy, and can spare some faith and devotion, you have a shot at being granted divine magic. Another advantage is that you don't need to understand how the magic works in order to use it, nor do you need to have much personal oomph to use it. Folks who would struggle to power even the simplest of arcane spells themselves can use terrifyingly powerful divine magic because it isn't coming from them, but their god.
Disadvantages: Divine magic is like a subscription service -- you don't really OWN that magic. If you cease to be faithful-- or your deity takes a sudden disliking to you-- you can be cut off from your magic in an instant. Furthermore, your power level is limited by the power of the deity you serve. Your local minor deity just doesn't have the heft of one of the big gods or goddesses worshipped by millions of people. The fervently faithful high priest of a small god is often no match for the casually reverent minor acolyte of a major deity. Also, deities can be kind of exclusive about their power. If a worshipper begins learning arcane magic as well, the deity may cut them off from divine magic, because if the worshipper is learning arcane magic... what do they need the deity's power for?
Nature Magic 
A wild, ill-defined, and poorly understood branch of magic that has few practitioners. A person doesn't 'learn' nature magic so much as they are 'mantled' with it. (Some would say 'infected' by it.) The most common source of nature magic that produces practitioners is Faeries, although in rare cases, other natural phenomena can produce practitioners as well. In the case of Faerie magic, a mortal wielding Faerie magic either made a deal with a Faerie and was granted a portion of their magic to use (known as a mantle), or was inflicted with a portion of that Faerie's magic, often largely for the Faerie's own purposes, or even simply their amusement.
Cost: Your humanity. Nature magic settling into a mortal body produces side effects in keeping with its own nature. For example, mortal bearers with Faerie magic are sensitive to iron, their spells can be dispelled with iron, and they are more prone to being .... evasive about the truth. The more power a bearer holds, the stronger the side effects.
Advantages: Almost zero learning curve. Nature magic functions on instinct. No one teaches bearers of Faerie magic how to create illusions, or summon wind, or breathe underwater... they just do it. They reflexively know how. They can potentially be very powerful, too. Nature isn't exactly a pushover. A bearer with a large mantle of power from their patron or source can hit hard, and pull on the inherent life energy of the world around them for more juice. Powerful nature practitioners can stand toe-to-toe with arcane archmagi and high priests of major gods.
Disadvantages: If your source/patron wants something from you, you're doing it. As long as you bear their power, your life isn't solely your own. Especially with Faeries, if they want something distasteful from you, and you refuse, they'll either force you to do it (marionetting you with their own power that's saturated into your body), or they'll strip their power from you -- an experience that is roughly equivalent to going cold-turkey from a highly addictive drug. A bearer abruptly stripped of their Faerie magic will often be willing to do LITERALLY ANYTHING to get it back, which usually results in them making even worse deals with their Faerie patron and getting even deeper into their debt. Other nature magic entities aren't necessarily as dangerous to deal with as Faeries... but anyone who has watched a nature documentary knows that nature isn't exactly trustworthy or gentle.
So yeah! Those are the three forms of magic in my setting. You'll see all of them eventually in the course of the comic. Right now, we're in chapter one, and the MC is the only person in her village who can't use the divine magic of the local deities... and no one knows why. This proves to be a bigger problem than it sounds.
