-	-	-	-	-
Alignment	-	-	-	DMG

Whether or not the character actively professes some deity, he or she will
have on alignment and serve one or more deities of this general alignment
indirectly and unbeknownst to the character. Changing of alignment
is a serious matter, although some players would have their characters
change alignment as often as they change socks. Not so!

First, change of alignment for clerics can be very serious, as it might cause a change of deity.
(See DAY-TO-DAY ACQUISITION OF CLERIC SPELLS.)
If a druid changes his or her alignment - that is, becomes other than neutral
-- then he or she is no longer a druid at all! Change of alignment will have
an adverse effect on any class of character if he or she is above the 2nd level.

Immediately upon alignment change actually occurring, the character
concerned will lose one level of experience, dropping experience points
to take him or her to the very beginning of the next lower level, losing the
hit die and/or hit points, and all abilities which accrued to him or her with
the lost level. If the alignment change is involuntary (such as that caused
by a powerful magic, a curse, etc.), then the character can regain all of the
losses (level, hit die, etc.) upon returning to his or her former alignment as
soon as is possible and after making atonement through a cleric of the
same alignment -- and sacrificing treasure which has a value of not less
than 10,000 g.p. per level of experience of the character. The sacrificial
amount is variable, so use your best judgment as to the total and what and
where it should go -- magic items to build up the NPC cleric, money out of
the campaign, magic items out of the campaign, etc. Similarly, such atonement
and sacrifice can be accomplished by a quest. Note that, in all likelihood,
the character will desire to retain the new alignment, and it is
incumbent upon you as DM to ensure that the player acts accordingly.
Some equally powerful means (divine intervention, remove curse, etc.)
must be used to restore the original alignment before atonement can
begin.

Characters who knowingly or unknowingly change alignment through
forethought or actions permanently lose the experience points and level
due to disfavor. They must also accept a severe disability in alignment
language during a one level transitional period. Until the character has
again achieved his or her former level of experience held prior to change
of alignment, he or she will not be able to converse in the former alignment's
tongue nor will anything but the rudest signaling be possible in the
new alignment language. (See ALIGNMENT LANGUAGE.) Although it is
possible for a character to allow himself or herself to be blown by the
winds as far as alignment is concerned, he or she will pay a penalty which
will effectively damn the character to oblivion.

A glance at the alignment chart will show that radical alignment change is
impossible without magical means. If one is chaotic good, it is possible to
change to neutral good or chaotic neutral only, depending upon desire
and/or actions. From the absolute neutral alignment one can only move to
some neutral-based alignment. This represents the fact that the character
must divorce himself or herself from certain precepts and views and
wholeheartedly embrace another set of values, and human nature is such
that without radical personality alteration (such as caused by insanity or
magic in the case of this game) such transition must be gradual.

It is assumed that the character's initial alignment has been his or hers for
a considerable period prior to the character's emergence as an adventurer.
This ethos will not be lightly changed by a stable, rational individual.
It is recommended that you do not inform players of the penalty which will occur with alignment change,
so that those who seek to use alignment as a means of furthering their own interests by conveniently
swapping one for another when they deem the time is ripe will find that they have, instead,
paid a stern price for fickleness.
 

Question: Does alignment change always require loss of a level?

Answer: Yes. See page 25, Dungeon Masters Guide. — W. Niebling, J. Ward
(Reminder: Unless 0-level rules are being used, a PC must be L2 or higher in order to lose a level from alignment change).