I have an idea for a Young Adult fantasy, a small number of teens are visited by characters from 'fantasy' world, at which point they learn that most of our fantasy worlds exist and that magic works in our present world. They are attacked by a few people selected by an enemy as their opposite number, also empowered by magic.
My big problem is guns getting in way of a more magical & sword vibe I want to go with. I'm okay with guns being present to some degree, but I don't want them to be the main characters primary weapons. I also don't like how instantly fatal they are. I want my heroes to be strong enough to have a significant effect in the world, but it doesn't matter how much magic they possess if a single sniper rifle can stop them effortlessly. Thus I would like to come up with some way of justifying the limited use of guns or cut their ability to completely neutralizer the protagonists.
It's a pretty straightforward plot as described above, other than the fact that it's going to have some actual death involved. In some ways, it's a partially deconstruct the standard YA magic hero story. The sudden presence of magic can't stay a secret and ends up being national news and even starting battles. The heroes can't resolve things without the use of force, there will be a need for some to be willing to fight and kill, and at least one of the heroes and some of their fantasy guides will fall in the fight. I'm not going entirely gritty deconstruction, some of the general YA optimism will exist and the teens won't be completely destroyed emotionally by the need to fight, but I am trying towards a more realistic Reality Ensues story while still keeping some of the YA tropes and general fantasy.
Lots of the fantasy guides are from Eastern Style RPGs, so think of any Final Fantasy to get a general feel for what the combat should be like. Lots of magic and swords and protagonist with a bit of Charles Atles Superpower when it comes to their skill with melee weapons.
The heroes all gain some level of enhanced physical fighting ability (the ways very, but generally fit under 'knowledge of fighting magically bestowed upon them' or 'prior training in actual martial arts or fencing, but with their magic abilities used to enhanced their physical skills'), with two characters playing the 'pure mage' role of no physical fighting skills.
One of the 'enemy' teens has a gift for bringing in people from other fantasy worlds. He declares himself the president of the US and starts bringing in the military from a fantasy world to enforce it. This military goes up against both the disorganized US government's military and our heroes as sort of 'mooks'. Generally, they're treated as less dangerous then our present military, but they have numbers.
My problem is that I want to try to justify a group of a few dozen, at most, heroes, all either larger than life fantasy heroes or teens with powerful magic, going up against a larger force of 'mook' soldiers. I want a real fight scene, so saying the teens just nuked everything with fire before the enemy knew what was happening is not really a possibility. the teens can do lots of 'weak' attacks, maybe toss a lightning bolt that zaps 3-5 soldiers at once, but they can't just nuke everything at once. I want a real challenge in such fights.
The enemy force consists of soldiers from a world that is a little past fantasy, but where swords and magic are used as often as guns. I'm going to claim that military tradition causes them to frown on guns and that a combination of limited gun crafting ability and armors that are effective against guns but not close range weapons all combined to lead to an emphasis on close range and magical fighting with guns used only to supplement the main force. However, OUR guns are still powerful, and it wouldn't take long for the enemy forces to realize they can go out and buy better guns at the local shop, or hire soldiers & mercenaries. How can I either limit adoption of our weapons or create a believable way to limit the power of adopted weapons?
The premise of this world is human belief in something can make it happen. The fantasy characters that come to our world to meet with the heroes come from real worlds that mimic popular literature because of the combined belief of people reading these literary works, and allowing themselves to imagine them as being real, was sufficient to make these worlds actually exist, giving life to the characters within them. The reason that our present world doesn't see any magic is that we all collectively believe magic shouldn't exist, and our collective belief in magic not existing keeps it from happening. However, if one person believes hard enough in something magical happening their one strong belief in something occurring can be enough to overcome the passive disbelief of others long enough to make the magic real.
The protagonists do not know this, they simply know that people showed up that shouldn't be able to exist and tried to drag them to a meeting without explaining why; only later did they discover they could work magic (having been inspired to believe in it by the sudden presence of so many other fantastical things). They were each selected by their creativity and ability to believe, effectively they were chosen as the teens most capable of using magic, but the fact that they don't know why they can do it limits their belief in their abilities and thus the power of their magic.
Each hero's magic feels very different because they each believe that magic should work differently, and each subconsciously places limits on what they can do because they believe those limits should exist. The enemy has been told how magic actually works and as such they better believe in their magic without limits and are therefore individually stronger than the heroes.