What properties of polymorph are inherited for the spell
polymorph any object (Player’s Handbook, page 263)? The
guidelines suggest that it overrides the normal rules for
creature type (an object isn’t any type of creature) and Hit
Die limits (turning a pebble into a human or a shrew into a
manticore, for example), but the spell doesn’t explicitly
describe the changes.
You correctly note that polymorph any object isn’t as clear
as it could be. The intent of the spell, however, becomes clear
by reading the accompanying charts. Polymorph any object
retains all the limitations of polymorph except as follows:
• It can affect an object, and also adds “object” to the list of
new forms allowed. It doesn’t add any more eligible creature
types for the new form (you can’t use polymorph any object to
assume the form of a construct, elemental, outsider, or undead).
• The assumed form still can’t have more Hit Dice than
your caster level (to a maximum of 15 HD at 15th level), but
the secondary limit of the subject’s original HD doesn’t apply.
A pebble (with no HD) or a lizard (with 1 HD) can be
transformed into any form whose HD don’t exceed 15 or the
caster’s level, whichever is lower. (Arguably, polymorph any
object should have a higher HD cap than polymorph, but that’s
not how the spell is written.) The new form can even have no
HD at all (as in the case of a creature polymorphed into an
object).
