Hearthstone director Ben Brode shed some light on a few Hearthstone mysteries in a new video from Ars Technica. The whole video is a good watch if you're interested in Hearthstone's history and DNA, but the best bit is right at the end, where Brode explains how Hearthstone got its fatigue mechanic, which deals escalating damage to players each time they draw cards after their deck is empty. As Brode explains, fatigue damage didn't always exist, and they only came up with it after Overwatch director Jeff Kaplan played Hearthstone for himself.
"We were doing a playtest and we asked Jeff Kaplan to come over and try the game," Brode said. "And he got really into it, he started playing minions and attacking, he was having fun figuring out what cards to play. He had never played it before, he was excited to get into it. And he was very close to winning, and then the computer he was playing against passed the turn. And it said 'Your turn, you lose!' And he was like, what?"
In the early version of Hearthstone that Kaplan played, fatigue damage didn't exist. Instead, when you ran out of cards, you automatically lost, like you do in other card games like Magic: The Gathering and Yu-Gi-Oh. The problem with this system, which Kaplan's feedback helped Team 5 realize, was that it could make a whole game feel pointless. "It didn't matter what decisions he made during the game, he was just going to lose because he ran out of cards," Brode said.
"So we designed the fatigue mechanic so that it ratchets up the damage every time you try and draw a card but your deck is empty," Brode said. "And what that does is connect back into the game. If you're one damage away from killing your opponent, he's going to die to fatigue. The whole game where you got him to that point mattered a lot."
Fatigue damage not only puts a hard cap on how long games can go on, it ties directly into the strategy of long matches. If you're playing a control deck against another control deck and you know the game is going to last a while, you might purposely avoid drawing extra cards in order to delay fatiguing.
Racing fatigue makes for some exciting photo-finishes, and the very existence of fatigue damage has also allowed for niche decks like Fatigue Rogue, Mill Druid, and most famously, Fatigue Warrior, a deck whose ability to "go infinite" and avoid fatigue damage entirely nearly led to tournament rule changes.