For Obsidimen, the 4e Goliath seems to be almost a perfect fit, so I will start there. In Earthsawn, the Obsidimen's stone like skin gives him or her fantastically tough natural armor - mechanically, they have the near equivalent of resist 3 weapon damage, which doesn't seem quite right for 4e. Related to the Obsidimen's natural armor is the downside of playing an Obsidimen. For cultural reasons, Obsidimen refuse to wear any non-living armor.
The Goliath's Stone's Endurance power is definitely on the right track here, and I will explore Obsidimen feats to enhance and extend the duration of Stone's Endurance, but I also will change the Obsidimen's racial defense bonus from the Goliath's +1 Will defense, to +1 Armor Class and +1 Fortitude defense. Both defenses are ones that Obsidimen should excel at, and the strict power gain of +1 Armor Class when compared to the Goliath, can be mitigated by requiring that the Obsidimen be wearing living or no armor in order for the bonuses to apply.
The 4e Goliath has an athletics bonus to jumping and climbing which does not seem normal for an Obsidimen, so that will get cut, and I will borrow a page from the Dwarf, and give Obsidimen a walking speed of 5 rather than 6 and the Encumbered Speed Dwarf racial trait.
Obsidimen
True as the Liferock from which they are born.RACIAL TRAITS
Average Height: 7' - 7' 6"
Average Weight: 800lbs - 1000lbs
Ability scores: +2 Constitution, +2 Strength
Size: Medium
Speed: 5 squares.
Vision: Normal
Languages: Common, Dwarven
Skill Bonuses: +2 Athletics, +2 Nature.
Encumbered Speed: You move at your normal speed even when it would be reduced by armor or a heavy load. Other effects that limit speed (such as difficult terrain or magic) affect you normally.
Stone-like Skin: You have a +1 racial bonus to AC and Fortitude when you are wearing no armor or living armor.
Stone's Endurance: You have the stone’s endurance power.
Liferock Heritage: You can take feats that have goliath as a prerequisite (as well as those specifically for obsidimen), as long as you meet any other requirements.
Stone's EnduranceObsidimen Racial Power
Your foes' attacks bounce off your stony hide.
Obsidimen connect with their fellows by returning to and merging with their liferocks where they share consciousness with their elders, in what they call, the dreaming. For the dreaming, I think the Deva Memory of a Thousand Lifetimes power is a neat way of representing access to the collected wisdom of the Obsidimen brotherhood. A paragon tier feat granting the power, and allowing access to other Deva feats allows a higher level Obsidimen the option to pursue that connection with the past lives of all their brothers who came before them.
The Toughness of Living Stone feat makes Stone's Endurance into a exceptionally strong power, but at the same time continues to push the Obsidimen to wear living armors.
The final two feats in this post, Improved Stone-like Skin and Strength of Stone continue to emphasize an Obsidimen's natural strength and toughness
Liferock Threads
Paragon Teir
Prerequisite: Obsidimen.
Benefit: You gain the Memory of a Thousand Lifetimes racial power, and you can take feats that have deva as a prerequisite.
Memory of a Thousand LifetimesObsidimen Racial Power
The dreamlike memories of your brothers lend insight to aid you.
Toughness of Living Stone
Prerequisite: Obsidimen, stone's endurance racial power.
Benefit: When you are wearing a no armor or living armor, your Stone's Endurance power gains the Sustain - Minor property, but each time the power is sustained the resistance drops by 1 (2 at level 11 and 3 at level 21).
Improved Stone-like Skin
Prerequisite: Obsidimen, stone-like skin racial trait.
Benefit: Your Stone-like skin bonus is increased to +2, to +3 at level 11 and to +4 at level 21.
Strength of Stone
Prerequisite: Obsidimen
Benefit: While you are wielding a versatile weapon, you gain a +1 bonus to damage. (So when wielding in two hands you gain a +2 bonus to damage).
