Runestones

Runestones are one of the cornerstones of diablo 3, they allow you to customize your skills changing their effect and power. Each color has it’s own effect which is different for each and every skill. The names were chosen to be ambiguous, while there is a bit of a ‘theme’ to each color they don’t have any specific effects assigned to them it could be anything.

 

Normal Nightmare Hell Inferno
Alabaster Runestone Alabaster Runestone Alabaster Runestone Alabaster Runestone Alabaster Runestone Alabaster Runestone Alabaster Runestone
Crimson Runestone Crimson Runestone Crimson Runestone Crimson Runestone Crimson Runestone Crimson Runestone Crimson Runestone
Golden Runestone Golden Runestone Golden Runestone Golden Runestone Golden Runestone Golden Runestone Golden Runestone
Indigo Runestone Indigo Runestone Indigo Runestone Indigo Runestone Indigo Runestone Indigo Runestone Indigo Runestone
Obsidian Runestone Obsidian Runestone Obsidian Runestone Obsidian Runestone Obsidian Runestone Obsidian Runestone Obsidian Runestone
Unattuned Runestone Unattuned Runestone Unattuned Runestone Unattuned Runestone Unattuned Runestone Unattuned Runestone Unattuned Runestone

 
Unattuned Runestones were a late addition, it’s still unknown how they will actually work upon release. Jay Wilson explained their ideas in this Interview on Diablofans.

So what we’re thinking about doing is essentially having runes dropped Unattuned, which means they’re kind of grey and generic, they don’t actually have a type. And then you pop them into a skill, and when you do that, the rune attunes to that skill; you can still remove the rune freely whenever you want, but now that rune is not an Indigo rune, it is a Magic Missile splitting rune. And on top of the Magic Missile splitting effect, it might give you a couple other affixes, like +10 Attack or something like that.
 
The reason we’re talking about doing that is, one, it…with the ability to kind of switch skills out, it would be nice to kind of have a soft mechanism that does make you want to focus on the skills that you want to focus on. When you have a rune that only has one effect on one skill, the point of comparison becomes a lot easier. And it really adds in the item game. It means that there’s really valuable rank 7 runes and meh OK rank 7 runes. And that’s something that we’d really like to see because it plays into how we want the item game in Diablo to play.

 
Examples:

Barbarian

Whirlwind is an iconic Diablo II skill, wherein the barbarian spins furiously and damages any enemies in his path.
 

Monk

Sweeping Wind is a combo skill that lashes out against all enemies surrounding the monk, creating a vortex of damaging wind that increases in damage and radius across three stages.
 

Wizard

Ray of Frost is a wizard spell that damages and freezes enemies caught in the beam, slowing their movement and attack speed.
 

Demon Hunter

Cluster Arrow is a powerful demon hunter tool, as it fires a cluster bomb which explodes on impact, releasing smaller bombs which explode shortly thereafter.
 

Witch Doctor

Acid Cloud is a witch doctor skill that summons an acid-spewing spirit, raining caustic, skin-dissolving death on the unfortunate enemies below.