What exactly do the magic skills do?

[Nanako]

I think destruction lowers the cost of destruction spells, but by how much? I want the actual numbers and mechanics

what -exactly- do each of the magical skills do?

[(J)]

As one becomes more experienced in Alteration, Conjuration, Destruction, Illusion, Mysticism, or Restoration, one does not receive bonuses per se, but rather, their skill level determines the strength of spells they can cast. The more experienced the character is, the more powerful spells that he or she can use.

[Nanako]

Originally posted by (J):

one does not receive bonuses per se,

I don't think this is correct

here's how it worked in the OG, from: https://en.uesp.net/wiki/Oblivion:Destruction
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As your destruction skill increases, the Magicka cost to cast destruction spells decreases, according to the following equation:

Cost = BaseCost * (1.4 - 0.012 * Min(Skill, 100))

The maximum value for Skill in this equation is 100; increases past 100 will not continue to decrease spell-casting cost.
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meaning a max level character would have their mana costs reduced by 80%

i'm really just asking if this has changed

[Googledebunker]

I know it allows you to learn more complicated spells, but I am still learning this as I go.