I've been following a story from 3.5e to 4e related to Nerull... but in 4e he does not exist! :o what happened to him in 4e?
Nerull trapped and tormented souls in Pluton (a domain of the Astral Sea in the Points of Light setting), plotting to become the king of the gods... until his mortal consort killed him and acquired his portfolio.
[She was] a haughty mortal sorcerer-queen whose death brought her into Nerull’s realm. The Lord of the Dead sought to bind her to him as his consort, but the sorcerer-queen refused him. Leading a rebellion of tormented souls, the queen overthrew Nerull, broke his hold on the dead, and claimed his portfolio. [Manual of the Planes 111]
She's now known as the Raven Queen. However, due to... reasons... the gods withheld her authority over the dead, so her powers are focused on death itself.
More details can be found in Divine Power and Manual of the Planes.