Erda

Erda was a Perpetual older than most myths, the geneticist who stayed with the Emperor after the others walked away, and the mother the Primarchs were not allowed to have. She helped make them. She watched the Crusade being loaded into their cribs. Then she opened a warp vortex, scattered her sons across the galaxy, and hid in Mauritania rather than watch them become weapons.

John Grammaticus found her at Guelb during the Siege and asked for a door into the Palace. She had none. She gave him Leetu instead, read the stars, and waited for Ollanius Persson, who did not arrive on her schedule.

Erebus offered her Chaos with four Greater Daemons for punctuation. She tore them down in three shapes and spat when he asked her to kneel. The athame finished the argument. The Emperor knew where she was the whole time and never came.