A dangerous, alien plane where glowing frog-slimes slither and slurp, metal-skinned bird people rebuff diplomacy, and only the endless subterranean tunnels are safe (just mind the gravity-bending moles). Visitors will have to skulk around in the dark to avoid the curse carried by the sunlight. Because (have I mentioned?) the sun is the source of a powerful curse--one that covers the whole planet.
Want to avoid fighter types focusing on swords? Make Longswords and Bastardswords the weapon of the Noble class, with a death penalty for other to carry. These weapons will be ornate and finally crafted. Adventurers will be stuck with cheaply made broad and shortswords, while professional fighters might use two handed swords.