Pocket Universe

After Superboy went onto the future to save the worldLex Luthor ,a noble scientist, created a lifeform from protomatter with Lana Lang's genetic material.

The Search

The shape changing Matrix was dispatched to a parallel world, hoping Superman would help. He answered the call and was forced to kill the three Kryptonians to save their world. Matrix was reduced to an amorphous mass in the fight. Superman brought Matrix to his world to recover on the Kent Farm. Matrix took on a feminine form and paid homage to her saviour by using her powers to become Supergirl. Due to her naivity, she fell under Lex Luthor's influence for a while, until she saw the manipulative criminal he is. She also had a brief stint in the teen titans.

Linda Danvers

Matrix saved the life of Linda Danvers, by merging there life essences. A new being was created with new abilities such as increased strength but reduced shape changing.

In time she discovered the violent life Linda had led and sought to redeem her. During her encounters with various supernatural entities, she discovered she was a reborn Earth-Angel. One of three on Earth.

She also lost her shapeshifting abilities as she began to see herself as just Linda or Supergirl. The part of her protoplasmic form that didn't merge became an insane creature and fought Linda/Matrix until she was absorbed by the Angel of Light Blithe.

Twilight

Matrix and Linda were eventually separated by Demon Queen Lilith. Matrix was guarded by a woman called Twilight. When Linda rescued Matrix after fighting and then gaining Twilight as an ally Twilight was fatally injured by Lilith. Linda convinced Matrix to bond with Twilight to heal her. Twilight/Matrix used her healing powers to restore Linda to her previous power levels. Twilight and Matrix whereabouts are unknown at this time.