Overkill

Overkill is an ability that activates whenever a card with the keyword deals damage to a character with less Health than the damage dealt during your turn. It was introduced in the Rastakhan's Rumble expansion.

Overkill-generating cards
This section lists cards which generate cards that have the ability to Overkill.

History
The ability that later became Overkill was originally experimented with during the development of Blackrock Mountain, where it was thematically tied to big and powerful Dragon minions and had the effect "Excess damage dealt to a minion is dealt to your opponent's hero" (a mechanic similar to the one later seen on the Explosive Runes spell). While this fit the vibe of feeling powerful and overpowering one's foes, it didn't offer much opportunity to make interesting choices — an element the team valued when designing the keyword — and led to it mostly being used in the same aggressive deck archetypes, leading to it being cut from the set.

Wanting to try the effect out a little bit more, the developers explored different versions of the ability during the development of The Witchwood, including one version known as "Splatter" which caused excess damage to splash to a random enemy minion. However, this led to questions such as "If Splatter's splash damage does excess damage to a minion, does the effect trigger again?", and if that was the case it felt odd having to track the damage as it bounced around to different minions. On the other hand, if the effect did not trigger repeatedly, it could sometimes feel like one's cards weren't effective when the excess damage splashed to the wrong enemy minion.

Finally, the team tried it again in the expansion that became Rastakhan's Rumble. After establishing the characters and setting of the expansion, Blizzard wanted to design a keyword that fit the fantasy of being "in the rumble" and decided that it's not simply enough to defeat one's oppontents; one has to style on them as well. Thus, they returned to the ability explored during Blackrock Mountain and The Witchwood and iterated on it until it became Overkill. An early version of Overkill would scale for each point of excess damage dealt; for example, dealing 7 excess damage to a minion with an Overkill card would result in gaining 7 Armor, drawing 7 cards, or similar effects. While this felt "okay", it felt bad to go up against this ability with smaller minions and ended up being a little bit "mathsy". Furthermore, it didn't allow the team to make Overkill cards that were as interesting, since there is only a small number of mechanics in Hearthstone that scale to a significant amount; for example, having an Overkill effect that summoned token minions could be problematic since the maximum board space is a mere 7 minions.

Eventually, the developers settled on having each Overkill card grant a different bonus when dealing excess damage to enemies and having the keyword be a purely binary effect with no scaling involved, since they found this to be the most fun version of the ability. In addition to ensuring that Overkill cards are used in many different types of decks, this allows players to demonstrate their skill by making decisions in various situations with different Overkill cards, as well as allowing them to brag by showing their opponents that they beat them by more than they needed to.

At one point, the team tested a version of Overkill that would allow it to trigger even on the opponent's turn (such as if the opponent traded one of their minions into the player's Overkill minion). However, they found that it "felt pretty bad" for the opponent, and also felt somewhat unnatural and at odds with the keyword's theme.

Thematically, Overkill plays to the gladiatorial spirit inherent in Rastakhan's Rumble's namesake gladiatorial event. In the words of Ben Thompson: "As a grizzled competitor of the ring, you know that the way to a fan's heart is through a dramatic flourish and some theatrical showmanship".

Patch changes

 * Added.