Skyrim “Arniel summon spell” issue

the-elder-scrolls-v-skyrim

I finished Arniel's Endeavors and got "Summon Arniel's Shade".

But there seems to be something wrong with it. It's just too good.

It costs me 0 magicka and he does not seem to have any health.

If I encounter a enemy that is too dangerous, I just let him loose and he battles the enemy for 60 seconds. Then, I can let him go again at no cost.

Is this a known issue?
It almost feels like cheating using him.

And is the quest over, or am I suppose to use him later in the game?

Best Answer

Summon Arniel's Shade is a powerful spell indeed. It costs 0 magicka and is immune to physical attacks. I'm not sure if the 0 cost was intended but it is certainly known.

This is the end of the quest.