Chrononine

In modern alchemical thinking, chrononine is a vital enzyme created in the body's temporal gland. This is the chemical that tells the body how old it is at any given moment. Apparently the more chrononine in the system, the older the body. Alchemical thought suggests that if the chrononine flow can be halted or even reversed, it would be possible to achieve eternal youth. Alchemists get very excited about this. But then, alchemists get very excited about anything that even hints at eternal life, even drinking their own urine.