Abyssal Rune

• Abyssal Rune
• Item Level 35
• Binds when picked up
• Unique
• Trinket
• +5 Haste
• Equip: Each time you cast a harmful spell, you have a chance to gain 590 spell power for 10 sec.
• Requires Level 30
• Sell Price: 10 73 43

Source

This item is found within the Trial of the Champion in both Eadric's Cache and Confessor's Cache.

Notes

• This item has a 25% proc chance.
• This item has a hidden internal cooldown of 45s.
• The definition of "harmful spell" is rather broad, and includes passive spell damage from buffs such as [Thorns] and [Molten Armor], as well as non-combat actions related to quests (like picking up chickens for Chicken Party!).

Effective Spell Power

The effective spell power granted by this item is affected primarily by cast time. This trinket benefits more from shorter cast times. The formula for calculating the amount of effective spell power granted by this trinket is:

E = 590 * 10 / (45 + (t / 0.25))

Where

E = effective +spell power 
t = cast time

The following Java Program can be used to obtain a table of effective +spell power for different cast times.

  public static void main(String[] args)
  {
      float time;
      float effective;

      for(time = 1; time < 6.5f; time += 0.5f)
      {
              effective = 590 * 10 / (45 + (time / 0.25f));

System.out.println("" + time + "" + effective + "");

      }
  }

This gives the results below:

Cast Time	Effective +Spell Power
1.0	120.408165
1.5	115.68627
2.0	111.320755
2.5	107.27273
3.0	103.50877
3.5	100.0
4.0	96.72131
4.5	93.650795
5.0	90.76923
5.5	88.0597
6.0	85.50725

Patch changes

• Patch 3.2.0 (2009-08-04): Added.
  

External links

• Wowhead
• WoWDB