Nap, may not be a bug

I saw in the academy that transmuters can learn to do it, but its not on the skill list. I use it, and get this You failed to calm your adrenaline. You are affected by: Spell: 'invis'. Skill: 'nap'. Cant practice it, not in my skill list...Is the academy transmuter room need updating or this skill need to be put on the list set?