How could a Druid make Dire / Legendary animals?

Hello,
My Druid player and I would like to make a way for him to be able to use his divine powers to transform his existing pets into dire and eventually legendary animals. He'd prefer one pet forever as opposed to ditching his pets as soon as he's outgrown them.

I posted this same question in the Rules forum because I don't know if 1e or 2e already answered this question, I can't find anything in 3e that actually explains what makes an animal dire.
That thread is here: http://enworld.cyberstreet.com/showthread.php?s=&threadid=20742

If this hasn't been covered, what would you suggest we do to allow him the ability to create dire and legendary animals?

I thought of making a spell that would sap some XP, but I am lost when it comes to deciding what level to make it.

Thanks for the help,
Telor

I'd suggest a spell like Awaken with an XP cost.

MotW has a rule variant that allows you to do soemthing like this, with XP expenditure and only to a certain point.

Personally, I think this is stupid. Why penalize a Druid for wanting to keep the same animal companion? If anything, reward him for roleplaying!

I just allow the animal companions of my Druids and Rangers to advance in accordance with the Ranger or Druid. At a certain point they can upgrade to Dire or Legendary. Seems to work so far. The animals almost become NPCs, in that the party no longer things of Farel, the panther, as a source of easy flanking, but an actual party member. They even bought him some magic items. Ain't they nice?

I've only had one druid in my game this far, so I don't have much experience in this matter. Anyways, I allowed her to keep the same pet around, giving the pet more hitdice as the druid gained levels, as not to make the pet less useful and more of a liability.

It worked out just fine. At one point the druid didn't want more HD for the pet for a couple of levels, so that he could Awaken it.

Well, you see, when a wildshaped druid and a dire wolverine love each other very much...

Seriously though, I think that "dire" is just a catch all for all those adjectives that used to pop up in front of animals like giant, carnivorous, Irish (deer). The dire animals are a whole different species. As far as pet upgrading goes, I would suggest one or both of the following. 1) a feat (along the lines of item creation) that allows one to increase the size of animals. This would cost xp (like magic item creation) but would be a permanent addition rather than an actual item. 2) Convince the DM to let your animal advance in HD (or even character levels).

P.S. If any zoological types out there want a headache, compare the stats of the wolverine and the dire badger.