Whirlwind

Whirlwind is a warrior spell card, inducted into the Legacy set, formerly from the Basic set.

Strategy
Whirlwind deals damage to ALL minions on the field, including friendly minions. It is a key warrior area of effect (AoE) damage card, since it has utility both as a form of multiple or even single-target removal, and as a way to activating damage-triggered effects, a key characteristic of the warrior class.

As removal, Whirlwind is a simple if two-sided effect, particularly useful with multiple small enemy minions on the board, as commonly used by aggro and zoo decks. The player must always weigh the damage to their own minions against the damage to the opponent's, making this spell most desirable when the player has few or no minions on the board, or when the enemy targets cannot be allowed to survive the turn.

However, Whirlwind truly shines as a means of activating damage-triggered effects, whether Enrage minions such as Raging Worgen and Amani Berserker, single-target on-damage effects like Axe Flinger, or wider effects such as Armorsmith or Frothing Berserker. Frothing Berserker in particular can make use of a single Whirlwind to immediately gain as much as 14 Attack, making the two cards a potentially game-winning combination, while Armorsmith can help mitigate the cost of playing Whirlwind with friendly minions on the board.

This card combos well with Battle Rage to damage everything on the board then draw a card for every damaged friendly character.

As a single point of damage, Whirlwind can also be useful for removing Divine Shield, in anticipation for more substantial attacks.

Lore
Whirlwind is a melee-range area of effect warrior attack. The warrior attacks all enemies within 8 yards in a whirl of steel, causing a percentage of weapon damage to each enemy. Whirlwind is an effective way of dealing damaging to multiple targets, and is only desirable when attacking groups of enemies. Unlike its appearance in Hearthstone, it does not deal damage to friendly targets.

Trivia

 * Early in the game's development, this card had the effect "Deal 1 damage to all enemies. If you have a weapon, +1 damage. If you are below 12 Health, +1 damage." This was eventually simplified to the card's current text, due to excessive complexity for players trying to learn and calculate the effects of playing the card.
 * The artwork for this card comes from the World of Warcraft Trading Card Game "The Hunt for Illidan" series, for the card Sweeping Strikes.

Patch changes

 * Moved from Basic to Legacy set.