High Density is the prequisite for Lithodermis. An increased density of tissue and bones that makes it more resistant to impact damage.
Another Maas Neotek mutation. Head to MK on the map. Sometimes there will be a Hepcat or two outside of the building, but if you're fast (and queue the movements) you can easily get by without having to go through them. Once inside, search around for a bit, then head down and mutate.
This mutation grants:
+3-5 beat resistance +1-4 bullet resistance
Easily one of the most popular mutations, usually reccomended to be picked up first, lets newbies beat on crackheads without a problem.
None, really. Just takes up a soak slot.