No probs
Also as far as im aware you have to be 70, but since the ability is present from lower level, it would lead one to assume there is another way of being able to use it.
Can try secret methods, such as using star (*) abilitiy twice then using a white potion then using star (*) ability once more, then casting Nocte Visus, grants what people call 3 star (*) invis. Similar to Hide skill. This can be combo'd with Sure Hit (a warrior skill), to grant upto 12 attacks without revealing yourself.
Many secrets probably more that no-one knows or will tell.