"Mother" Was a Smoke Monster by johnfisch

When the MIB is down in the well working, we see Mother watching from a distance. Then we focus on the MIB as he works his coals.

The next thing we hear is the clank clank noise that always precedes the smoke monster. Suddenly Mother appears at the bottom of the well.

After she knocks out the MIB, she transports him to the surface, turn into smoke, fill in the well and then kill all of the Others.

Without any doubt she had once upon a time after she arrived on the island, she also went into the light and she was, perhaps, the original smoke monster.

We know that to kill the smoke monster you need to do so before it speaks which is exactly what the MIB did to Mother. She was ready and expecting to die.

When Jacob pushed his brother into the light, he emerged as a new smoke monster. The new smoke monster is a hybrid of the island light and the predominate characteristics of Jacob's brother, i.e. wants to leave the island, vengeful, now hates Jacob etc.