Large swaths can be attacked by rapid-fire tandem casting of Ice Storm.

The Adept-level area effect missile spell, Ice Storm, is distinct from its counterparts in the other two elements in that it covers an area of effect as the projectile itself travels, instead of just projecting its effect area upon impact. The Deep Freeze perk is useful, but almost exactly the same effect can be achieved with dual-casting and Impact. Vampires have a bonus 50% Frost resistance and Nord vampires are completely immune, as are all Dwarven automatons. Unfortunately, many enemies boast a resistance to Frost damage, and Nords-the most common NPCs in Skyrim-resist it as well. Causes enemies below 20% health to be paralyzed. Slows targets by 50% for a few seconds (duration varies).Deals damage to health and stamina (typically the same amount).Middle magicka cost of the three elements.With Dragonborn installed, Ignite is much more magicka-efficient, but will not advance your Destruction skill very quickly. This trick also works well when combined with the Slow Time shout. It should also be noted that even without Aspect of Terror, Flames is the second-most magicka-efficient spell in the base game (after Firebolt), and Aspect of Terror will make it an uncontested first place. If you take the Aspect of Terror perk from the Illusion skill tree, it will make this trick even more devastating and potentially viable even at high levels despite being a Novice-level spell. In addition, by casting the Flames spell repeatedly in short bursts, you can apply the 'on-fire' effect several times, which will dramatically increase your damage output. The Intense Flames perk is of limited use, firstly because humanoid enemies will drop down to their knees when their health is below 10%, and secondly because enemies that do not drop down will run away, forcing you to kill them some other way. In some dungeons there are pools of flammable liquid which you can ignite with fire magic, resulting in impressive conflagrations that can wipe out enemies in seconds, particularly at low levels. Many inhabitants of Skyrim are weak against fire damage, including trolls and all creatures with 'Frost', 'Ice', or 'Snow' in their name. Causes enemies below 20% health to run away. Sets targets on fire, usually dealing an additional 10% damage over 1 second, but some spells do more.Lowest magicka cost of the three elements.Since some enemies are resistant to particular forms of magic, anyone relying on Destruction is well-advised to learn spells from more than one element, and perhaps to specialize in two or more. Destruction mages can use perks to specialize in one or more of the elements-fire, frost, and shock-gaining the ability to do extra damage. Destruction is the principal damage-dealing school of magic.

Skyrim destruction master quest