Throws a fiery ball that causes (65% of spell power) Fire damage.
Rank 3 (Level 41): Damage increased by 15%.
Rank 2 (Level 33): Each time your Fireball fails to critically strike a target, it gains a stacking 10% increased critical strike chance. Effect ends when Fireball critically strikes.
The basic fire spell which all followers of the Orcish cults (the underworld) first learn. It channels the flames of Hades through the caster's body, allowing the wielder to direct it as a missile at anyone he chooses. It is a dangerous magik to employ, but the effects seem to delight even the lowest circle of Warlock to no end.[1]
Magiks involving the cardinal elements of the universe are favorites of the Mages. The Fireball is launched from the palms of the Mage and streaks like a comet blazing across the battlefield - slamming its fiery bulk into whatever stands in its path.[2]
Trivia
Fireball is a basic Mage spell in Hearthstone. The flavor text reads: "This spell is useful for burning things. If you're looking for spells that toast things, or just warm them a little, you're in the wrong place."
Patches and hotfixes
Hotfix (2016-08-26):Fireball (Fire) now deals 75% additional damage in PvP (was 150%).
Patch 7.0.3 (2016-07-19): Damage increased by 30%.
Patch 5.0.4 (2012-08-28): Now a Fire specialization ability.
Patch 4.3.2 (2012-01-31): Fireball damage has been reduced by roughly 6%.
Patch 4.3.0 (2011-11-29): Damage increased by approximately 17%.
Patch 4.0.6 (2011-02-08): Mana cost has been reduced to 9% of base mana.
Hotfix (2011-01-18):The mana costs of the following mage spells have been reduced, but they still require the previous percentage of base mana in order to be cast: [Arcane Barrage] (11% of base mana), [Arcane Blast] (7% of base mana), and Fireball (12% of base mana). As an example, Fireball requires 16% base mana to cast, but only consumes 12% of base mana.
[Critical Mass], 
[Firestarter], Firestarter (mage honor talent), 
[Tinder]
[Mastery: Ignite].
