This discussion feels so specific to my current reading mood. After bouncing between a few fandoms lately, I keep circling back to the way certain characters from other worlds just slot into Tamriel with a satisfying click. Not every crossover has that chemistry where the mechanics of both settings genuinely interact instead of just a coat of paint.
A pairing I stumbled upon that shouldn't work but absolutely does is 'The Legend of Zelda' meets the Dwemer. Link as a wandering adventurer encountering the ruins of Kagrenac's people, using his Sheikah Slate to interface with tonal architecture. The author treated the ancient Dwemer tech almost like a new type of Sheikah relic, and having Link navigate the political chaos of Morrowind's Great Houses felt more organic than I expected. The best part was how they handled the silence of the gods—both worlds share that theme, but the tone is so different.
Another is a fusion where the Soul Cairn from 'Skyrim' becomes a destination for characters from 'Fullmetal Alchemist'. The Homunculi, born from forbidden alchemy, facing the Ideal Masters who trade in souls. I read one where Envy gets trapped there and has to confront what it means to be a constructed being in a realm full of them. It was bleak, but the philosophical clash was executed with a precision most crossovers lack.
I suppose what I look for is a mutual alteration of both worlds, not just dropping one character into another. The pairings that linger are the ones where the rules of magic or reality from each side have to negotiate, and the characters react to that dissonance.
Man, the lore-blending in those crossovers is where things get wild. They often start from a premise that just breaks a character from another universe into Tamriel, or vice versa. But the thoughtful writers dig into the metaphysics. Like, is the Thalmor's belief about ascending to divinity through unmaking the world compatible with, say, the Force from 'Star Wars' as a cosmic energy field? I've seen some fics treat the Elder Scrolls themselves as objects of prophecy that could interact strangely with other world's fate-weaving systems, like the Pattern in 'The Wheel of Time'.
What's tricky is reconciling the sheer density of TES lore—the dragon breaks, CHIM, the godhead—with settings that have simpler rules. A good writer doesn't just smash them together; they find a friction point. One memorable story had a Dragonborn in Westeros, and the magic didn't just work—it slowly bled into the world, altering it, because that's how reality in TES often behaves. The lore isn't a backdrop; it's an active, corrosive element. That's when it feels authentic, not just a costume party.