In older versions of RQ, we often had a Special Ability of "Permanent [Spell]", for instance Permanent Protection 4 or Permanent Ironhand 6, which had the effect of a particular spell but the effect was permanent and could not be dispelled.
There's no reason why you couldn't have the same thing in RQM using a Legendary Ability. You'd have a different Legendary Ability for each spell effect, or you could just have a single on Permanent [Spell] that you could get multiple times.
They wouldn't just be learned as normal Legendary Abilities, though, they would definitely come under the "Gained as a Gift from the Gods", "Gained on a HeroQuest" or "Gained as a Magical Side-effect" categories.
There's no reason why you couldn't have the same thing in RQM using a Legendary Ability. You'd have a different Legendary Ability for each spell effect, or you could just have a single on Permanent [Spell] that you could get multiple times.
They wouldn't just be learned as normal Legendary Abilities, though, they would definitely come under the "Gained as a Gift from the Gods", "Gained on a HeroQuest" or "Gained as a Magical Side-effect" categories.