Amethyst Powder

The guidelines said I can't post multiple suggestions in one post, however these two go hand in hand and don't really work without eachother so I hope it counts as one technically

What would Amethyst Powder do exactly? I figured it could be used to create a barrier that Allays and Vexes can't fly through. They can still fly around it, unless they're trapped in a ring of Amethyst Powder. The inspiration came from salt being used to trap ghosts

How can this be used? Well, I've heard Vexes were annoying to deal with and this would be a way to deal with them without breaking immersion and using a boat. It's an extra layer of strategy when facing off the Woodland Mansion. That, and this leads me to the second idea that goes with this:

Currently, Allays are trapped within cages and cannot fly through walls like Vexes can. With Amethyst Powder, it could be used to trap Allays in these areas to keep the exploration aspect of having to find them whilst also allowing them to fly through walls. An Allay being able to fly through walls will be extremely helpful for people to find their death spot if they're uncertain where it is but know a general location

What else could Amethyst Powder do? Maybe you could tip arrows with it for added damage to Phantoms and Ghasts. I'm not entirely sure on what else though sadly