Stampede

Rain of Vengeance (known as Rain of Arrows prior to August 2011) is a Hatred Spending Demon Hunter skill unlocked at Level 29.

An Alabaster Rune placed in it will have the following effect on the Demon Hunter's attack.

Stampede

[e] Summon a wave of 14 Shadow Beasts to tear across the ground, knocking back enemies and dealing 126% weapon damage.

Skill Design

The basic skill emulates the "massive wave of arrows" type attack that's popular in medieval and martial arts films, with various demonic/magical modifications from the skill runes. You can see all six functions in the movie below. Turn it up to 1080HD, and play it full screen for the best visuals.

Note that this video was obtained via data mining with an emulator. It was not released by Blizzard and there will likely be some modifications to the runestone effects in the final game.