I have a few questions about these spells for anyone who has gotten the chance to use them:

1. How long does the "wall" last on the ground and keep doing damage? I want to play as an archer who draws people to me into traps. As such, I might cast a wall spell on the area near me, shoot a few arrows at people, and then once the enemies start running at me, I'll be able to draw them into a zone where they'll be taking a lot of damage (provided I have a good choke point to place it in where the enemies will stay there). The process of drawing them there will take time though, so if the wall dissipates after a few seconds, then I shouldn't bother.

2. If I have the illusion perk that makes spellcasting silent would I be able to cast this spell around while sneaking as long as no one actually sees my character? This would help me get the spell into the best position.

1. wont last long enough for that

2. yes

Does that mean it only lasts 5 seconds or more like 20?