A Color-changing Swarming Mob for the Sift

A mob encountered in the Sift.

They spawn around their hive block. There are about 15 in a hive, but that could change.
When a player right-clicks the hive block with an item in their hand, it starts the process of copying it. The hive doesn't take the original item.

The swarm then arranges itself into the silhouette of a random item, and each mob changes its colors to represent a color in the item. Together, the swarm forms a collective image of an item; since there's only about 15 of them, it's a bit of a guessing game for the player.

The pool of items they pick from for the image only consists of exotic, exploration-based items. Things like music discs, armor trims, echo shards, bottles o enchanting, etc. It's nothing that can be farmed or grinded for. Valuable resources like diamonds, or rare grinded-for things like totems of undying or nether stars, aren't in the pool.

The player then has to go out into the world and find this item. The progress and image of the swarm persists while the player is exploring.
When the player brings back the item (by dropping it), it adds progress to the hive. The rarer or more expensive the player's original item was, the more brought-back items it costs.

When the hive is finally done, it spits out an exact duplicate of the original item.

This concept is great because it provides an alternate route to grinding for expensive items, and instead allows the player to explore their world for it.
It also provides a vanilla method of duplicating items.