Increase creature size by one step

[demi123]

Is there a way to permanently change a medium sized creature into a large creature?

 

[Zurai]

Enlarge Person can be made permanent via Permanency. There's also the half-minotaur template for LA+1 (which is horribly broken, btw).

 

[Jhaelen]

Enlarge Person can be made permanent via Permanency. There's also the half-minotaur template for LA+1 (which is horribly broken, btw).

Well, the former can be dispelled, the latter cannot be applied to an existing creature. I don't know of any good way, except:
Get reincarnated as a bugbear! (unfortunately only a 1% chance...)

 

[Caliban]

Is there a way to permanently change a medium sized creature into a large creature?

Are you asking as a player or as a DM?

Because a DM can just advance a creature one size category (giving it +1 CR) using the rules in the back of the MM, and make up whatever in-game reason he wants for it. (Creature is a mutant, creature is cursed, side effect of a magical accident, template, etc.)

 

[demi123]

I am asking as a player.

 

[Caliban]

I am asking as a player.

Then the previous posts are probably what you are looking for.

 

[frankthedm]

And do note, the enlarge person only effects humanoids. And if you permanency that spell, if you ever drop an item, it shrinks back down with no way to re-enlarge it.

Plus the permanency can get dispelled.