Situation: The cleric of Pelor was held against his will, and forced to become a vampire. Pelor is known for especially hating the undead, but also "urges his followers to remember that excessive attention to things of evil can blind one to the truly important things: compassion and goodness" as Wikipedia says. The cleric is also repentant and remains devout.
In the monster manual, vampires are "always evil", however it is noted that "always [alignment]" simply means it is exceedingly rare to find a creature of [not that alignment]. Let's say the cleric is able to stay within 1 alignment step of Pelor by some miracle (pun unintended).
Questions: Does anything happen to his spell casting? Will he need to find a new deity that's willing to accept undead followers?
(Inspired by the question https://rpg.stackexchange.com/questions/82431/implications-of-cleric-becoming-undead, which was closed as unclear.)
Best Answer
If the cleric were truly repentant and devout, he would arrange for a resurrection, and immediately destroy himself. However, let's say he was on his way to do just that. I know of no RAW reason that, say, a True Neutral vampire cleric could not receive spells from Pelor - Libris Mortis, the Monster Manual, and Complete Divine don't say anything about the issue. It will be challenging, however: from page 15 of Libris Mortis:
The book doesn't go into any details, so it is the DM's job to decide what problems an undead worshiper of a "mortal" god encounters.
There is an article in Dragon magazine #346 that suggests the origin of vampires was clerics of Pelor that turned away from him to study black magics:
So the DM has a ton of plot hooks for a vampire Pelorite.
Mechanics of a vampire cleric of Pelor
Vampire clerics are severely hampered, regardless of the god they serve: