Rune of mangroves passive?

Hi, my newest character is going to have a few runes tattooed onto her to give her a few abilities. However, I'm not sure on how to use of rune of the mangroves. Is it passive? Or is it an ability type?

Edit.

The rune in question grants immunity to all non-magical poisons and diseases.

"Simple runes flicker with suppressed energy until the runemaster
needs their power, then they blaze with brilliant potency"
Page 12, More magic & Mayhem, Warcraft RPG Book

Is it passive? Or is it an ability type?

It is a passive that activates into a blazing glow when it power is needed - so in this case, whenever you come into contact with any non-magical poison or disease.

In other words, it is a passive with a flashy spell effect when the conditions for its activation are met.