Serra is a minor god, the God of Apathy. Worshipped mainly by the neutral, her name is used in the phrase "Oh, Serra Serra, whatever will be, will be, will be."
No one knows why there is a third, superfluous "will be". When questioned, worshippers of Serra merely reply "meh".
It's extremely rare for people to formally change from another god to start worshipping Serra - normally, they can't be bothered going through the process. As such, Serra has the most unofficial worshippers of all the Gods.