Well

From A Wheel of Time Wiki

A Well is a ter'angreal that is able to store the One Power so that a channeler can use it as a separate source.

Conceivably, an Aes Sedai could use this while shielded since it works inside another ter'angreal that cuts off the True Source. It can also be used to channel inside a Stedding. The only two known Wells are owned by Nynaeve al'Meara and Cadsuane Melaidhrin. The Eye of the World was also a well, however its current status and location are unknown.