Empty air sandwich
Terrarian
I swear I have the feeling that you could outright remove it from appearing in the underground and it wouldn't even matter
Obviously for some time it's better than anything you have because it's above gold, and it's like a particularly rare ore that only shows up in small amounts because of that, but if you find it underground, you'll need GOLD pickaxe to mine it first, so you might not even be able to get it if you find it, and it completely loses its value to get it underground after you beat the naturally-spawning Eye of Cthulhu for the first time, where you become able to get it the good way with very generous amounts.
And if you mine it you only get like 4 ore per dump. That's 1 bar. You need to have at least EIGHT to make a bow out of it (10 if you want the sword). And the only things you can actually make this way are ore weapons (and a fishing rod), there is the important pickaxe and an armor set but those are locked out for the meantime because those also need a material from Eater/Brain. So technically you can grind for the super rare ore to get a post-gold basic weapon that would be cool if you want, but by the time you would actually collect enough you probably already got 500% past the point of being unable to beat the mandatorily-appearing Eye of Cthulhu who basically gives you all of it at once and lets you know you can just talk to his cousin to get more. And after that you can still see veins of it underground but it's not even worth the time to dig it out, legitimately worth less than iron or web. Despite being a rare ore you only see sometimes who even lights itself up for you to get.
If it didn't spawn in the underground at all that might even just be polishing clutter... But imagine if it was the other way around as something actually really cool worth rarity, like if it was replaced with a new ultra-rare ore called rainbowite that you can use as a joker card to craft it into your choice of various items, and they can upgrade over progression with materials, but each craft and each upgrade needs more and more rainbowite, that's available throughout the entire game in the underground if you just get lucky enough to find more from any incidental exploration, being useful even through hardmode as a special ore.
Obviously for some time it's better than anything you have because it's above gold, and it's like a particularly rare ore that only shows up in small amounts because of that, but if you find it underground, you'll need GOLD pickaxe to mine it first, so you might not even be able to get it if you find it, and it completely loses its value to get it underground after you beat the naturally-spawning Eye of Cthulhu for the first time, where you become able to get it the good way with very generous amounts.
And if you mine it you only get like 4 ore per dump. That's 1 bar. You need to have at least EIGHT to make a bow out of it (10 if you want the sword). And the only things you can actually make this way are ore weapons (and a fishing rod), there is the important pickaxe and an armor set but those are locked out for the meantime because those also need a material from Eater/Brain. So technically you can grind for the super rare ore to get a post-gold basic weapon that would be cool if you want, but by the time you would actually collect enough you probably already got 500% past the point of being unable to beat the mandatorily-appearing Eye of Cthulhu who basically gives you all of it at once and lets you know you can just talk to his cousin to get more. And after that you can still see veins of it underground but it's not even worth the time to dig it out, legitimately worth less than iron or web. Despite being a rare ore you only see sometimes who even lights itself up for you to get.
If it didn't spawn in the underground at all that might even just be polishing clutter... But imagine if it was the other way around as something actually really cool worth rarity, like if it was replaced with a new ultra-rare ore called rainbowite that you can use as a joker card to craft it into your choice of various items, and they can upgrade over progression with materials, but each craft and each upgrade needs more and more rainbowite, that's available throughout the entire game in the underground if you just get lucky enough to find more from any incidental exploration, being useful even through hardmode as a special ore.