Saw on the loading screen that theres a spell called "Magic Wall", suppose to harm/kill anything that passes through it. Any tips on location? Cost for buying? School of magic?

--Archmage Durza Stormblade Rasleen,
Master of Magic

Well, I think it's the group of Expert Destruction spells, which are Wall of Storms, Wall of Flames and Wall of Frost. Their respective spell tomes can be bought from Faralda after getting a skill of 75 in Destruction.

http://www.uesp.net/wiki/Skyrim:Wall_of_Flames#Wall_of_Flames

Yea see I thought about that, I have all of those spells but the way the game described it made it seem like it was its own individual tome... :/