A tiny vial sized sample was procured from the End of Time bar on Kalpa 3, where it was occasionally sold in drinks to keep them permanently cold. It is considered a form of ‘perfect’ cold, similar to Phlogiston is to normal fire. Similarly, it is a form of Anum.
While bitterly cold to the touch, it has already been separated from its source so it will neither spread nor break down on its own. It can be used to eliminate Phlogiston (albeit slowly, given the size of the sample) by overwriting the existing source. It would appear the perfect elements only cancel either other out when they freshly intermix, not when they’re applied in sequence.