Greetings, travelers!

This thread aims to help new creators to know when to use certain keywords. In order to do this, we will classify all existing keywords in different classes, according to the sets where they can be used. So far, Blizzard has only broken these rules twice, so if you want to make a believable card, following them is surely a good place to start.

@Mods, if you believe this post should be included in the Fan Creations Primer thread, go ahead :)

Basic keywords

Extensive list: Battlecry, Charge, Divine Shield, Freeze, Spell Damage, Taunt.

These keywords can appear in any set, including the Basic set.

• Poisonous is not included here, because it was introduced in Journey to Un'goro, so it's classified as Evergreen.
• Divine Shield only appears in Neutral and Paladin cards, with the only exceptions being Al'Akir the Windlord and Elixir of Purity.
• Freeze only appears in Neutral, Mage and Shaman cards.

Classic keywords

Extensive list: Choose One, Combo, Counter, Deathrattle, Immune, Overload, Secret, Silence, Stealth, Windfury.

These keywords can appear in every set, except Basic. They expand the Basic ruleset to make Hearthstone more rich and complex.

• Choose One, Combo and Overload are exclusive to Druid, Rogue and Shaman, respectively.
• Windfury is exclusive to Neutral and Shaman.

Evergreen keywords

Extensive list: Discover, Poisonous, Lifesteal, Rush.

These keywords were introduced in a particular expansion, but have also appeared in later sets. If previous cards had that effect, they are modified to include the keyword (see Emperor Cobra or Queen of Pain)

• Poisonous is included in the Basic set in the HoF replacement Plaguebringer. This sets a precedent for using Evergreen keywords in that set, although I don't think Discover would fit the Basic set.

Expansion-exclusive keywords

Extensive list: Spare Part, Inspire, Jade Golem, Adapt, Death Knight, Recruit, Echo, Magnetic, Overkill, Twinspell, Reborn.

These keywords only exist in the expansion they are introduced. If previous of later sets include cards with similar effects, they are worded explicitly (see how Meat Wagon and Captain Hooktusk don't use Recruit, even if their effect is just that).

• Before the introduction of SN1P-SN4P, Echo used to belong to this category.

Year-exclusive keywords

Extensive list: Echo, Lackey.

These keywords can appear in all cards of a certain Year. While Lackey was a year-exclusive keyword by design, the inclusion of Echo in this category is more or less accidental, since the only card that doesn't belong to The Witchwood with this keyword is SN1P-SN4P.

Recurring keywords

Extensive list: Mega-Windfury, Quest, Choose a Deathrattle, Casts When Drawn, Choose Twice, Start of Game.

These keywords appear in expansions from time to time. All of them are very different in nature, however:

• Mega-Windfury has only appeared in two cards in total and has always been a very marginal part of the expansion.
• Quest, on the other hand, has always been one of the core aspects of the expansions they appear in.
• Casts When Drawn is a token-exclusive keyword.
• Choose a Deathrattle and Choose Twice are variations of the Druid-exclusive keyword Choose One. For synergy purposes (like Ossirian Tear), Choose a Deathrattle is considered a Choose One card, while Choose Twice isn't.
• Start of Game was a core aspect in The Witchwood. The appearance of this keyword modified the text of a previously existing card, Prince Malchezaar.

Quote From Demonxz95

Quote From Wailor

• Divine Shield only appears in Neutral and Paladin cards, with the only exception being Al'akir, the Windlord.

And Elixir of Purity (one of Unidentified Elixir's forms). I don't blame you for missing this one though.

Right, thanks. I only checked collectible cards

For people learning what these words/phrases mean, it's better to define them before using them. 

EG: "Poisonous is not included here, because it is classified as Evergreen"

What is "evergreen"?

Quote From frenzy

For people learning what these words/phrases mean, it's better to define them before using them. 

EG: "Poisonous is not included here, because it is classified as Evergreen"

What is "evergreen"?

Thanks :)

I  that sentence to be more understandable. Did you notice some other similar case?