Lithodermis

    The color in the player's skin slowly grows darker in patches until he/she looks a light
    blue-grey. He/She claps, producing a rocky sort of thud.
    [ You've developed the 'lithodermis' mutation! ]

Lithodermis is the upgrade to High Density. Your skin becomes more dense and stony, helping you resist broken limbs, knockouts, beatings, falling, and brain damage. However your added weight impairs climbing and swimming and weighs you down, decreasing how much you can carry.

Location

In Adamant Canyon. From Luskentyre Plateau, go down and travel southerly within the depths of the canyon until you come upon the mouth of a cave. To be more specific, go down into the depths of the canyon and south, then southwest and south, until you can go down to the breach. From here, the map cuts out, but you want to go southwest then south for a while (there's a small river), and after crossing a rope bridge going south a bit more then east a tiny bit and you'll be there. The only real foes are rock leeches and the occasional ghost. It's a good idea to set ropes down on every climb, since with Lithodermis you'll likely be overweight and/or too low in climb to get back. Alternatively, you could just run through naked and grab the mutation then suicide by drowning or such.

Effects

This mutation grants:

    -3 to Climb
    -3 to Swim
    +70 generic broken limb resistance
    +60 knockout resistance
    +50 brain damage resistance
    +1-2 beat resistance
    +2-2 bullet resistance
    +25kg to player's weight (12.5kg to carried weight)

Advantages

This is a decent choice for characters with low Endurance, who'd otherwise easily suffer knockouts. Added beat and bullet soaks are great, because these are two of the most obnoxious damage types; beat can break bones and stun, while bullet tends to come in thick and can't be dodged well. Knockout and broken limb resistance is good to have, especially for PvP. The resistance to brain damage is the least impactful bonus, but it's convenient, and good for those with no friends to perform surgery on them.

Lithodermis synergizes exceptionally well with Hooligan. Between the two, you can hit 90% knockout resistance, which will save you from the vast majority of hits that would otherwise knock you flat. Lithodermis also buffs the damage of any headbutts you hit by simply making your head heavier! If you find yourself on the receiving end of a headbutt, Lithodermis will also help protect you with its beat soaks, and the knockout resistance will again help stop you from being flattened.

Another cool advantage is that fall damage is reduced noticably, so your climb handicap will rarely get you killed when you fall. Keep in mind that you can still land on your head, or your armor might take damage. As a rule of thumb, falls of about 10m or less are usually safe. Other unlisted bonuses are a bonus to damage when using your bare fists as well as the inability to be tattooed by a tattoo gun! You can still get that tramp stamp you've always wanted by using an engraving tool in place of a tattoo gun.

Disadvantages

Knockout resistance aside, the overall bonuses are nothing mindblowing.

The -3 to Swim and Climb are annoying but no big deal, as those skill raws are very cheap and plenty of people go for Salamander. However, you are hard-locked out of Leapfrog (and, by extension, Flight) if you have Lithodermis.

Litho adds 25kg to your weight (which is sometimes annoying when flying in a plane with low weight capacity), which also makes you able to carry 12.5kg less (it's halved since it's "worn" weight). This extra weight is not shown in the inventory screen, which takes some getting used to. If you're a brawny character, it's hardly much of a problem, but others may want to pick up Mule. The 30% bonus to carry weight from Mule almost perfectly matches the 28% or so that Lithodermis can add. That also makes it nigh impossible to take stress from Mule by not carrying enough, given your passive weight.

Appearance

    His/Her skin has a bluish grey hue.