(YORISHIRO) An object which attracts divine spirits (
souls) or which acts as a media through which these spirits manifest themselves. In episode 26',
Kouzou Fuyutsuki refers to
Eva-01 as a
"Medium" (
Well of Souls) when
SEELE uses it to create the
Tree of Life.
Source: The End of Evangelion : Glossary contained within The End of Evangelion - Theatrical Program.