Regenerating limbs? You don't say? I would rather enjoy imagining that. Yes, if you could post the code, that would be lovely. So, if, as dustman pointed out, the buffalot is still feeble, how may I go about making it more durable? Also, is there any way that I could make it drop adamantine when it is butchered? Maybe as a EBO?
During the body transformation limbs are regenerated as well as any other injury. So I think regenerating code just temporary transforms T1000 to the same creature.
And for butchering check material token BUTCHER_SPECIAL Wiki says "Specifies the item type used for butchering results made of this material."
Try to add [BUTCHER_SPECIAL:BOULDER:NONE] to INORGANIC:ADAMANTINE material. To make all butcherable parts made of adamantine material become boulders adamantine items after butchering.
OR you can add [BUTCHER_SPECIAL:BOULDER:NONE] directly after specific materials like [USE_MATERIAL:BONE:INORGANIC:ADAMANTINE] in your creature definiton.
For example (altered part of your code):
[USE_MATERIAL:SKIN:INORGANIC:ADAMANTINE]
[BUTCHER_SPECIAL:BOULDER:NONE]
[USE_MATERIAL:BONE:INORGANIC:ADAMANTINE]
[USE_MATERIAL:HOOF:INORGANIC:ADAMANTINE]
[USE_MATERIAL:HORN:INORGANIC:ADAMANTINE]
[USE_MATERIAL:TOOTH:INORGANIC:ADAMANTINE]
Instead of skin you will get adamantine stone after butchering and bone, hoofs, horns and tooth made of adamantine.