- Not available on that edition (the reason is in the tooltip)
- Depends on the setting, your class or another addon (details in the tooltip)
What it does
Checks how many runes of the type you choose are ready to use, compared with the number you set.
Why you might use it
For Death Knights on Classic progression (Mists), compares how many runes of one type (Blood, Frost, Unholy or Death) are ready right now. Use it to spend runes before they cap, for example Obliterate when both Frost and Unholy runes are up, or Blood Boil only when a Blood rune is free. It does not exist on Classic Era, TBC Anniversary, Retail (which has one generic rune pool) or WoW Forever. See also Rune Cooldown and Power.
Example
the number of Unholy runes available is equal to 2
Settings
What each setting in the condition editor means, from the game's own help.
Rune Type - Which type of runes you wish to check.
Blood
Unholy
Frost
Death
Operator - How to compare Runes with the Runes value. This comparison uses basic mathematical comparison operations.
Runes - The number of runes currently available.