Verified answer

You have a 8% chance of carving it from the tail, and a 10% chance of getting it in the rewards if you capture it. Your chances are slim, but if you sever the tail and cap it enough you should get it eventually. If you are hunting the diablos in high rank then your chance of getting Diablos Marrow are increased. Your chance of carving it becomes 12% and your chance of getting it in the rewards for a cap will become 14%. It is a rare item to get from diablos, even at a high rank, but if you hunt this guy enough you should eventually get one.

This Site Might Help You.

RE:

Monster Hunter 3 ultimate Diablos Marrow?

I need Diablos marrow to upgrade my weapon, and i was wondering how to get it exactly. I have been killing the low rank and have been cutting off the tail and carving it, and checking the rewards after killing the Diablos and all i get is tail casings...

I know you have to cut off the tail but can...

The desire sensor is set on high. Lower it by 'not' wanting the item you are looking for.

That or capture it.

Also, it's monster hunter. You're supposed to spend a lot of time looking for certain items.

Happy Hunting!!

Monster Hunter Diablos