One sad thing that I have noticed over the years is when Reincarnate/Reincarnation come up, people automatically think it only applies to PCs and is some way to screw over players. It is like no one ever considered the potential of the spells in designing a setting or culture, especially if the spells use different charts from the standard ones provided. There could be:

- A royal family being reincarnated over and over to keep in power

- Druids wanting to be animals to gain a better understanding of why they protect nature

-         Wizards rewarding their weak servants (kobolds, commoners, familiar’s family) with nifty and powerful new forms after they die

-         A druid punishing a red dragon by turning it into a small mammal for the destruction of a forest

-         Or a dragon that turns its fallen dragonic foes into puny humanoids

-         Lochathah or tritons taking land lubber forms to explore the surface world

-         A clerical version that turns foes of the faith into the god’s sacred animal

-         A magic-user turning enemies into spirits of magic that teach new spells

-         Druids that cast Reincarnate on the flensed carcasses of a community’s livestock to either create monsters to terrorize them or to create more food to reduce hunting pressure

-         A magic-user’s laboratory that contains jars of pickled punks that animate when freed and then reincarnate when slain

-         A beholder mage that replaced one of its eye rays with Reincarnation and thus has an unlimited number of prey creatures to hunt while wandering its prison

-         Nagas and sphinxes that use the spell to transform creatures they slay into allied guardians

-         A renegade devil that is bypassing the normal routes to power by reincarnating mortals into subservient devils, specialists that can weaken the master’s foes

-         A magic-user who is using Reincarnation to corrupt druidic blood rituals, bring back sacrificed animals and tainting the result of the rituals in the process

-         Land that rejects the dead, reincarnating them all

-         A necromancer who has a version of Reincarnation that turns the dead into random undead, which can bite him in the rear if the results is something that he can not control

-         A yellow musk creeper that implants several seeds- after each is planted, the victim is reincarnated into a new “zombie” form and spreads the next seed

-         Frost giant shamans use Reincarnate to turn dead slaves into arctic monsters to terrorize human(oid) communities

-         Fairy dragons turn dead animals into living party creatures (possibly animated objects) that help with their pranks and other fun making

-         A iron golem variant that turns dead intruders into valuable creatures, such as carnbuncles, golden gorgers or yellow urchins, so that their creators can harvest such wealth

And why use Reincarnate or Reincarnation over Polymorph (any Object)? Simple, the former spells are permanent and the only way to get back to one’s original form permanently is with Wishes or equally powerful quests. In fact some of those examples are based on that. In 3e and later editions Reincarnate does not work on unwilling creatures, yet the red dragon may wish to be a squirrel and get the chance to regain its former glory rather than be reduced to a larva, potential lich food.

So there is a lot of potential for spells that bring long life and new forms for characters, be they player character or not.