Each player starts the game with a full deck of 30 cards. All cards drawn are drawn from that deck, slowly depleting its supply of cards. The player's hero will announce when the deck has only one card left, and again once the deck is fully exhausted.
Once a player has exhausted their deck, trying to draw a further card will cause Fatigue, dealing damage to the 英雄. This includes cards automatically drawn at the start of your 回合, and cards specifically drawn as a result of other 过牌 effects. Fatigue takes effect each time a card is attempted to be drawn.
Fatigue deals 1 damage to the hero, plus 1 damage for each time Fatigue has already dealt damage to the player. Fatigue therefore deals damage cumulatively, steadily increasing in power each time it deals damage.
Fatigue only deals damage when the attempt to draw a card fails. If the player restocks their deck, such as through shuffle into deck effects, the player will not suffer fatigue when then successfully drawing a card. However, Fatigue never resets. This means that even if the player restocks their deck, or successfully draws cards, the next time they fail to draw a card, Fatigue will pick up where it left off, dealing 1 more damage than it did the last time.
Because Fatigue is caused by the attempt to draw a card, not the movement of the card itself, similar effects such as put into hand effects, put into battlefield effects, discard effects and remove from deck effects will not trigger Fatigue.
- Fatigue acts to limit games' length, and also provides a conclusion in the unlikely event that both heroes end up with no cards and no minions on the battlefield.
- In long games, Fatigue may act as a deterrent to drawing cards too quickly earlier in the game. Players who have used many extra-card drawing effects such as Arcane Intellect will find themselves facing Fatigue sooner than their opponents. However, the advantage of drawing cards more quickly usually outweighs the drawback of risking earlier Fatigue.
- Players can mouse over their own and their opponent's deck to display how many cards are remaining in each. This is particularly important to keep in mind when using effects or abilities that allow you to draw extra cards.
- If both heroes take measures to survive for this long, the game ends in an unconditional draw at the start of the 90th turn, even if both players are Immune.
- Fatigue cannot be reset - for example by adding cards back to your deck, or replacing your hero.
- Fatigue can be calculated with the formula ((N)(N+1))//2 with N being the number of the highest fatigue damage taken whilst drawing.
- From Patch 126.96.36.19957 (2015-09-29) until Patch 188.8.131.5233 (LoE patch), a bug caused replacing your hero (such as by using Lord Jaraxxus or Majordomo Executus) to reset your Fatigue, so the next Fatigue damages for 1 again.
Some control decks may employ Fatigue damage as a secondary or even primary means of winning games. Mage decks excel at this approach, thanks to multiple board-wide Freeze effects, delaying secrets like Ice Block, and a large range of removal spells. Players can also force the opponent to overdraw through effects such as Acolyte of Pain and Coldlight Oracle, while keeping their own card draw low. Effects like Alexstrasza's Battlecry can be useful for late damage when having focused on stalling until that point, allowing Fatigue to push the opponent over the edge.
- This effect is based on fatigue, a mechanic from World of Warcraft. Fatigue causes characters traveling through or over very deep water to become exhausted, eventually suffering substantial damage every two seconds. Fatigue is usually only incurred when attempting to cross oceans or swim between continents, and prevents players from swimming between the major continents, bypassing normal travel requirements, or reaching areas that are intended to be inaccessible, such as GM Island. Fatigue can usually be avoided by traveling by land or shallower waters; in some cases players may skirt fatigue in order to shorten their travel, but move back into shallower waters before they suffer fatal damage. In a few cases fatigue cannot be avoided, but players with sufficiently fast flying mounts are able to travel through the fatigue zone before they succumb to its effects. In these cases, fatigue acts as a limited barrier to travel between certain areas.
- The amount of fatigue damage caused by each draw can climb at least as high as 14745.