First you have to join the mages guild then keep doing quests until you are accepted into the arcane university,i dont exactly know where to find the spell making altar but i do know somebody will probobly tell you(excuse my spelling and hope this helps)
There are 2 places you can make a spell. The Arch Mages Quarters and a building on the far right of the Arcane Univercity.
To create spells either get Frostcrag Spire, or get into the Arcane Universty by fufilling all the local mages guild requirments.
I would suggest the Mages guild in Bruma, they specialize in conjuration. Or Eril's Mysteries if you have Shivering Isles. I hope I helped!
Cast spells
If you mean to create spells you need to join the mages guild andget into the arcane university and find the right room with the alters of spellmaking in the but if you have the wizards tower upgrade then you just need to buy the magnletow candles and put the in the alter and you can create spells! Hope this helped :)
Cast a lot of alteration spells.
You will always have a spell in use on Oblivion. If you don't want to use that spell, then simply select a different one. :)
You cannot construct your own spells as you could in oblivion, you must find or purchase spell tomes and consume them.
The dark elf is very good for spells.
It should be in the list of all your other spells. Cast it normally.
30 second invisibility
They are in all of the cities mages guild mostly or in the ARCANE UNIVERSITY.
To kill any kind of ghost or spirit in TES 4: Oblivion, you need to either use spells, or enchanted, silver or daedric weapons.
They use special effects to create the awesome spells on Harry Potter.
There isn't one. There is only weakness to fire, frost, shock, magic, and normal weapons spells in oblivion. There is a weakness to disease spell in Morrowind, i think.