Rain of Vengeance (known as Rain of Arrows prior to August 2011) is a Hatred Spending Demon Hunter skill unlocked at Level 29.
An Indigo Rune placed in it will have the following effect on the Demon Hunter's attack.
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Dark Cloud |
[e] Launch a massive volley of guided arrows that rain down on enemies for the next 12 seconds for 56% 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.