Frost Nova

Frost Nova is a level 3 point-blank area of effect mage spell that does light damage and freezes all enemies within 12 yards of the mage, rooting them in place for 8 seconds. Rooted enemies have a chance to break out each time they take damage; this check is made every time damage is taken from any source.

Improvements

 * Chilled to the Bone (honor talent)

Tips and tactics
At its simplest, Frost Nova can be used to allow the mage to escape. Targets that are not damaged after Frost Nova may well stay frozen for 8 seconds. When overwhelmed by additional mobs or finding your health running low, try to draw all mobs into melee range before using Frost Nova, and escaping to safety.

Frost Nova is also a critical mage ability in kiting, preventing melee enemies from reaching the mage and dealing damage. When kiting mobs, wait until the mob is within melee range before using Frost Nova, then make the most of this by escaping to the longest range your spells can reach from, and re-commencing your assault. This reduces spell pushback and damage taken by the mage, and is a good skill to master for PvP and trickier encounters. This is not as effective against caster-type enemies, where abilities such as Counterspell are more effective at reducing damage. You can also use Frost Nova in PvE to root enemies that you may have pulled off the tank, allowing them time to regain aggro.

As well as its obvious kiting uses, Frost Nova is also an extremely important damaging ability for mages with Shatter. This talent potentially trebles the critical strike chance of attacks made against frozen targets, as well as improving Frostbolt by a further 20%, dramatically increasing damage dealt to the frozen target(s). Used skillfully this can allow the mage to deal large amounts of burst damage very quickly, while the target is frozen in place.

Ice Lance is another ability that works with Frost Nova, dealing three times as much damage to frozen targets.

Trivia

 * Frost Nova is a basic Mage spell in Hearthstone. The flavor text reads: "Hey man, that's cold. Literally and metaphorically."
 * Frost Nova is one of Kel'Thuzad's basic abilities in Heroes of the Storm.