Gareth left the little frightened village of Nightfall in the company of disreputable, but tenacious and well armed mercenaries, to search the drow caves for boys that had gone missing from the village. Gareth was the only one that had returned alive.
The mercenaries had managed to ambush a small Drow escort partol. Gareth, being a trader and jack of all trades, not a fighter, stayed back to observe. The mercenaries suffered some losses, but out numbered the drow so overwhelmingly that they managed to win. Helping sort through the bodies and loot for his half of a fighters share, Gareth found a necklace on a Drow preistess, and the pendant was a small boy’s hand. When he showed the necklace to the mercenaries, they had laughed and said “One more good reason not to return. We’ve already been paid, but messengers bringing bad news get no reward.”
When Gareth had objected, the mercenaries had knocked him out and bound him, leaving him for spider bait for when the Drow searched for their patrol. Having no rope, they improvised bindings out of coils of stranger Drow rope they had found.
Gareth had awoke bound and gagged with his mouth dry from his injury. He struggled in his bonds, but when they didn’t give, he had bit down on his gag in frustration. To his surprise it had given some, and to his larger surprise, the chewing moistened his mouth, letting him taste the material that had been used to gag him. It was heavenly.
Gareth had chewed though his gag, almost with regret, and then carefully bitten through his bindings before collecting them and all the material he could find and returning to town.
He let the villagers know thier children were dead, and barely managed to get out of town with out being lynched, and then traveled to major cities and traded off his rare food stuff to the most exclusive and high class chefs in the land.
It does not confer any special drow powers, any resistance to posion, you can’t see in the dark, you don’t turn into a spider or drow or anything interesting.
Since it is just a foodstuff, the drow have never seen the need to put any “disintergrates in sunlight” magics on it. It spoils as fast as jerky normally spoils.
It’s delicious food, though. If you manage to be on friendly enough relations with a drow to ask them about it they’ll say “What do you expect us to eat? Slugs and mushrooms? We have lots of spiders, our god provides them you see, but do you have any idea how bad they taste? We are elves still after all. You wouldn’t believe what you have to do to make a giant spider taste good.”