Spool

A spool is the core of one's spiritual energy where they store their essence. Their Soulthread is wrapped around their spool and spread throughout their body to allow them to collect aura and perform techniques. One's spool is located just below their naval and just as one intuitively feels that their thoughts emanate from their head, so too does one's flow essence come from their spool.
Every Weaver has a limited capacity which determines how much essence/ki they can use before needing to rest and restore themselves.