Thermos

Thermos is the all-purpose Stamina regeneration upgrade: +15% regeneration, with no condition about extracting, items or abilities. Using the resting rate of 2.4 per second from the Statistics page, that is 2.76 per second, so refilling a 100-point bar takes about 36.2 seconds instead of 41.7, a saving of roughly 5 seconds per full refill. The gain scales with how often you drain the bar, which makes it more helpful in long runs than in short ones.

Next to Star Pillow it looks modest, because Star Pillow gives +100% but only while extracting. Thermos works while you hide, walk or wait in the elevator, which is why it is the better partner for Toons that spend more time away from machines. It does not change maximum Stamina, so a 1-star Toon still starts from 100.

The requirements ask for patience rather than skill: 1250 Ichor, surviving 50 floors and picking up 50 items. There is no Research on any Twisted involved. It is available in the Store today.