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.