Based on the previous answer here, concerning hammer-proof armor, one of the easiest way to mitigate blunt force trauma, both from swinging hammers and falling off buildings, are with some sort of dampening soft material. However, a hay bale big enough to pad such blows would have to be pretty thick, being able to deform at least 20 cm, meaning that it needs to be thicker then that, according to the answer.
So, how would one go about creating a condensed version of such hay bales, so that the dampening force is a property of the material, rather than the size and structure of it? The material should preferably be sort of metallic, so I can say they can be forged into stuff, although any other material would work fine.
I am seeking a science-based answer, assuming you could modify the properties of matter with magic. EG: You take a piece of steel and you slide its sheer strength up, or tone down its brittleness.
Price is of no concern, in fact, such a material would be glorious and should not be easy to make.