Many of the amulets and rings that wizards (for example) wear are not “magic per se” but rather mana pools to give them additional mana reserves in combat. The wizard who makes the mana pool has a link to it and they can charge it or draw on it as needed.
There is also, I will say, an analog of this for deities and their avatars called a God Pool. It’s a giant well from which deities and their servants can draw power, and to which avatars funnel mana from priests from worshipers into.
I’m curious can demons have mana pools as well?