If you want to change your skills and spells in Diablo III, all you have to do is use a very shiny stone.
Last year at BlizzCon, we caught our first glimpse at Diablo III's Runestone system - a way to further customize your character's abilities beyond simply putting points into them as you level up. Attaching a different rune to an ability will change how the ability functions, such as the witch doctor's "Plague of Toads" spell, which with the proper rune will instead summon a single Giant Toad that devours enemies and vomits up loot.
The Irvine-based developer has released a series of videos that further elaborates on the runestone system by taking one ability from each of the game's five classes and showing how it changes when attached to the five types of runestones: Crimson, Indigo, Obsidian, Golden, and Alabaster. (Come on, guys, you couldn't think of a cooler word than "Golden"?)
Whirlwind is an iconic Diablo 2 skill, wherein the barbarian spins furiously and damages any enemies in his path.
*Crimson - Shoots bits of rock and gravel in every direction, dealing area effect damage.
*Indigo - Barbarian spawns smaller whirlwinds which deal direct damage.
*Obsidian - Provides the barbarian with immunity to immobilizing effects.
*Golden - Reduced Fury cost.
*Alabaster - Critical strikes confuse enemies, forcing them to attack their allies for a short time.
Monk's Sweeping Wind
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.
*Crimson - A flurry of blades increases Sweeping Wind's damage.
*Indigo - Expands the area of effect and strikes enemies with additional fire-based attacks.
*Obsidian - A persistent whirlwind surrounds the monk, dealing damage to any foes that come into contact.
*Golden - Increases Spirit regeneration.
*Alabaster - A powerful sandstorm billows with the monk's attacks, damaging enemies and knocking them back.
Wizard's Ray of Frost
Ray of Frost is a wizard spell that damages and freezes enemies caught in the beam, slowing their movement and attack speed.
*Crimson - Beam increases in damage the longer it remains in use, to a cap.
*Indigo - Wizard is surrounded by a swirling vortex of sleet, damaging any foes that come into contact.
*Obsidian - Decreases beam damage, but increases reduction in target movement and attack speed.
*Golden - Arcane Power cost reduced.
*Alabaster - Enemies slain by Ray of Frost have a chance to leave an area of ice on the ground where they die, damaging other enemies if they move through it.
Demon Hunter's Cluster Arrow
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.
*Crimson - Increases the damage of the explosion at the point of impact.
*Indigo - Fires enemy-seeking missiles instead of grenades.
*Obsidian - The Cluster Arrow is launched high into the air and rains down grenades.
*Golden - Instead of grenades, the skill spawns shadow creatures that attack nearby enemies and leech life to the demon hunter.
*Alabaster - Adds a stun effect to the grenade explosions.
Witch Doctor's Acid Cloud
Acid Cloud is a witch doctor skill that summons an acid-spewing spirit, raining caustic, skin-dissolving death on the unfortunate enemies below.
*Crimson - Causes immediate damage instead of a damage over time effect.
*Indigo - Increases area-of-effect radius.
*Obsidian - Spawns slimes that attack nearby enemies.
*Golden - Afflicts enemies with a disease effect that deals damage over time.
*Alabaster - The witch doctor belches forth a directional pool of acid.
Though this isn't displayed in the trailer, we also know that the runestones themselves have levels which may further effect the spell. For instance, attaching a level 1 Indigo rune to the Wizard's basic Magic Missile spell will make it shoot one extra missile per cast, but attaching a level 7 Indigo rune will make each cast of the spell shoot a whopping 8 projectiles.
With the runestone system - not to mention the different skills, traits, enhancement, charms and the like - it's no wonder that Diablo III has a whopping 97 billion different class builds. And that's before you even get into armor, weaponry, gems, and the like.
This game will consume lives, people. I'm not even joking.
For more on the runestone system (and others), check out our Blizzcon 2010 interview: The Art and Design of Diablo III.