Gummy Worm

This is a permanent fishing power boost, once per character, and the only way to make one is to get a Gold Worm into Shimmer. Gold Worms turn up underground in place of ordinary ones at a rate low enough that you stumble into them rather than farm them.

The mistake is using it as a worm. A gold one is excellent bait and it sells for a decent amount, and both are tempting when you are standing there with a rod in hand. Neither is worth as much as a stat that follows you for the rest of the run. Bring it to Shimmer and drop it in.