Destruction is THE most annoying skill to level up IMO (speech is maby secound). I should probably google some more or read UESP maby.

But having the DG crown witch let me have mage stone and lover stone. And then having sleep bonus. I only leveled Destruction from 25 to 26 1/2 with only using chain lightning in a whole dungeon level. Like really?!?

I had ones legendary destruction skill and know fire storm can level up destruction 1-2 levels after each usage against one enemy pre level 50-60ish.

But how does destruction leveling work? Will it level up faster if I also use a fortify destruction potion or...?

http://www.uesp.net/wiki/Skyrim:Destruction Gaining Skill XP

• The XP gain for Destruction skill is dependent on the base magicka cost of the spell and the damage inflicted on a target. Thus, increasing the difficulty level will slow down skill development, as your damage output will be lower. Lowering the difficulty below Adept (gaining bonus damage) will not increase the XP gains. Dual Casting does not increase XP gain.
• To level this skill, you must cast a spell on a valid target. This can be exploited by casting the spells on essential targets that will not turn hostile. Some of these targets include http://www.uesp.net/wiki/Skyrim:Shadowmere, http://www.uesp.net/wiki/Skyrim:Hadvar or http://www.uesp.net/wiki/Skyrim:Ralof during http://www.uesp.net/wiki/Skyrim:Unbound, the http://www.uesp.net/wiki/Dragonborn:Riekling_Chief during http://www.uesp.net/wiki/Dragonborn:The_Chief_of_Thirsk_Hall^{http://www.uesp.net/wiki/Dragonborn:Dragonborn}, http://www.uesp.net/wiki/Skyrim:Esbern before http://www.uesp.net/wiki/Skyrim:A_Cornered_Rat, http://www.uesp.net/wiki/Skyrim:Paarthurnax_%28dragon%29 before starting http://www.uesp.net/wiki/Skyrim:Paarthurnax_%28quest%29, http://www.uesp.net/wiki/Skyrim:M%27aiq_the_Liar, http://www.uesp.net/wiki/Skyrim:Ancano before the conclusion of http://www.uesp.net/wiki/Skyrim:Revealing_the_Unseen, conjured creatures, and http://www.uesp.net/wiki/Skyrim:Torture_Victim.
  • Note that the target in question must actually sustain damage for it to count. For this reason, casting spells on invincible targets such as http://www.uesp.net/wiki/Skyrim:Child and http://www.uesp.net/wiki/Skyrim:Brynjolf will not level your skill.
• http://www.uesp.net/wiki/Skyrim:Regenerate_Magicka effects help reduce downtimes while training.
• It is possible to reduce or even completely eliminate the magicka cost of spells by stacking http://www.uesp.net/wiki/Skyrim:Fortify_Destruction enchanting effects. The http://www.uesp.net/wiki/Dragonborn:Secret_of_Arcana^{http://www.uesp.net/wiki/Dragonborn:Dragonborn} power does the same thing, but only for 30 seconds.
• Casting Blizzard will increase Destruction Skill even if there is no opponent. Since the spell does a small amount of damage to you, this appears to count as a valid opponent. Although you can only obtain Blizzard at skill level 100, if you subsequently make your Destruction skill http://www.uesp.net/wiki/Skyrim:Skills#Legendary_Skills, you can then use Blizzard to level it.

Except I've found that Ancano does turn hostile when I cast a destuction spell on him. Or does this mean only during that specifc quest and not afteward? Haven't tried som of the others yet.