Potions of Plenty

 is a side quest in.

Synopsis
Neale, the potion seller in the arena, is working on a project concerning Kazuwari's abundant soul essence. He enlisted the Watcher's aid as a research assistant and gatherer of samples.

Walkthrough

 * The quest can be completed while fighting through the Crucible's challenges and requires you to wear Neale's belt during the fights. The device will automatically gather samples of the ambient soul essence and will need to be returned after being charged. This produces an upgraded belt, which then needs to be worn to face the tougher challenges, and so on, and so forth. Naturally, selling or dropping the belt fails the quest.
 * If you've completed all of the trials but still need more belt energy, you can repeat previous trials.

Belt stages and rewards
 * You're first rewarded with the Skull of the Fallen, a reusable potion that grants +30 health, once per rest. Neale uses the collected essence to upgrade the belt to Less Unstable Coil.
 * Next Neale will reward you with the Bubbling Chalice, a reusable potion that grants +10 Freeze Armor Rating and will cause melee attackers to suffer 8-12 burn damage. It lasts for 45 seconds, and is usable once per rest. He then upgrades the belt to Least Unstable Coil (its final form), however it still needs to be fully charged.
 * Finally, Neale will reward you with Liquid Adra, a reusable potion that grants you the affects of a random potion or unguent, usable once per rest.