Remembrance

All those jars have the same substance, even if it doesn't seem so. It's just that it comes in different... shapes. I think the easiest way to explain it is by comparing it with the states of matter that exists in your world. In this case, some states are slightly different or somethig completely out of the forms that you could understantd, but it's more or less the same principle... I think. I haven read a book of physics in a long, long time.
Each shape has different properties that define how it is applied, the time it takes for the process to be completed, and the duration of the results, but they all fulfill the same purpose: fight unnecesary or inconvenient decay of magical items and useful ghosts.
That one... no, no, the dark one that looks like an oinment. That's the best for varnishing hard tools, or to turn delicate surfaces into strong ones. It doesn't add any new characteristics, just a barrier that keeps decay, and sometimes damage, away.
The cube in the corner is Remembrance too—blocky remembrance, it's called—, but it's only used to build safety boxes. Probably in the other extreme, you have the liquid type, which is used to modify the item to which it is applied, very useful. For example, it can be used to turn the leaves produced by the Symbiosis drums, to turn them into a version of themselves that would pass for jewerly even before being turned into beats

Access & Availability

A team of biologists has been designated to produce enough of the substance for any necessary use.

Utility

It stops the time induced decay in ghosts and in parts of plants. It's often used to create items or new ghosts based on leaves, flowers and simple ghosts that would be damaged by the environment where they are needed.