What is Dormant in Hearthstone?
Hearthstone has many card effects that are common enough that they get their own keyword - a word or two that immediately tells you how the card works. Let's take a look at the Dormant keyword.
Dormant is a mechanic where a card takes up a minion slot on the board, but is otherwise not counted as a minion. It was first seen during the Party Portals! Tavern Brawl on August 31st 2016, and was seen the very next day. in One Night in Karazhan during the fight against the Shade of Aran. The mechanic was first made available in Constructed formats in Journey to Un'Goro, and the mechanic was made a keyword in Ashes of Outland.
Keywords that Work Great with Dormant
As Dormant minions are not truly minions in any way and cannot be interacted with and have no effect while dormant, there is no way to directly support them.
Playing Against Dormant in Hearthstone
The Dormant minions in Ashes of Outland (the "imprisoned" cards) all take 2 turns for them to awaken with their effect, giving you a little bit of time to prepare for their arrival and withstand their effects better.
Other Dormant minions which wake up via a gameplay condition (Sherazin, Corpse Flower, The Darkness, Lucentbark) cannot attack when they awaken, always giving you a turn to react to it. Sherazin and Lucentbark can also infinitely regenerate themselves (provided the resources to do so are available), so a Silence can permanently take care of them.
Nether Portal can be strong, but it's slow, taking multiple turns before its effect starts to become strong. In this case, you can possibly end the game quickly before they get out of hand. The Imps are also fairly small, meaning that many board clears can get rid of them.
If Maiev Shadowsong is used on an "imprisoned" minion, its effect will reactivate when it reawakens.
Example Hearthstone Dormant Cards
Sherazin, Corpse Flower is the first card that introduced Dormant to Ranked play. As long as the Rogue is able to play 4 cards in a turn, Sherazin can infinitely resummon itself.
The Darkness is one of the most infamous cards in the game, as it skips its Battlecry if it's cheated into play. As of the Ashes of Outland patch though, this is no longer possible. The Darkness will shuffle 3 Candles into your opponent's deck when it's played. When all 3 of them are drawn, it will awaken as a 20/20 for 4 mana. As strong as that sounds on paper, its lack of immediate impact on the board, tempo loss, and overall slow speed falters it. Its best shot at being used is to counter Highlander decks as all of their Highlander cards will be inactive until they draw at least 2 of the Candles.
Imprisoned Antaen is an "imprisoned" minion from Ashes of Outland. When it awakens, it will deal 10 damage in the same vein as Avenging Wrath in addition to playing a 10/6 on the board. It's also the quickest nerfed card in the history of the game, lasting less than 2 days before getting nerfed.
[Hearthstone Card (Lakarri Sacrifice) Not Found] will create a spell in your hand that opens a Nether Portal when you discard 6 cards.