Lilith

Lilith is "the" focal point of the Evangelion series. She is crucified in the Central Dogma right inside the GeoFront, impaled with the Lance of Longinus that somehow prevents her severed legs to regenerate.
Dripping from her is blood, which forms a sea of LCL (Link Connection Liquid), which is used to ensure connection between Evangelion and it's pilot.
Lilith is the source of human life, while Adam is supposed to be the source of angel life, but that topic is open to discussion (some sources state, that Lilith is "mother" to the angels as well.).
As well could it be discussed whether Lilith should be considered an "angel", as she was on earth long before Adam arrived ... if the angels had to follow a certain "order" of appearance, that would maybe make EVA the second angel, as she was cloned from Adam. This relates to mythology, where Lilith was supposed to be Adam's first wife. She is considered a demon and because she was banished before the exile, she wasn't made mortal either.
She was either worshipped as source of life or as a night-spirit... better known as vampire.
It is said that Lilith had several children with the archangels, these children were demon's as well and were called Lilim.
As Unit 01 is a direct clone of Lilith, both play an integral part in the Human Instrumentality Project, the unification of mankind as a single, pure being ... or simpler put genocide by Third Impact.