Try tinkers construct. It allows customization of powerful weapons and tools.
If you want a battle type mod there are a few I know.
1: Battle towers. Adds towers that you can fight to the top in, and topple them to the ground when you beat them.
2: Better dungeons. Adds more dungeons to the game.
3: Midevil warfare. It allows you too basically make an army of your own, and attack other armies. I think it will go well with your theme.
There is also millenair (I think that's it's spelling.). It adds more villages to the world, and you can trade with them, fight the villagers, do quests for them and more. They even will expand them selves, farm, and mine even. It's a good mod if Minecraft seems too dead.
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