The Paladin is one of the nine hero choices for the Hearthstone card game. A player who picks this hero can use the Paladin cards as well as neutral minions.
The internet provides many examples of Paladin decks. But it can be difficult to find a broad overview of how the class works. This essay aims to fill that role.
Section One: Behaviors
The Paladin cards include several that interact with your draw pile (Blessing of Wisdom, Crystology, Call to Adventure, Prismatic Lens, Duel, and Bellringer Sentry) to make your deck predictable and efficient.
Only two Paladin cards interact with your discard pile (Immortal Prelate and Kangor's Endless Army). These each define their own deck archetype as described below.
The Paladin cards include only three that interact with your hand (Glowstone Technician, Bronze Herald, and Dragon Speaker). These currently are fun but not a key feature of any meta deck.
No Paladin cards interact with battlecries. This is an intentional weakness for the hero.
The only Paladin card that interacts with deathrattle is the secret Redemption, which allows a minion's deathrattle to occur an extra time. Small but significant!
Currently Paladin cards have a creature type synergy with mechs and dragons. In the past murlocs and recruits were too, but no longer.
Filling your side of the battlefield with small minions is called a "wide board". Some other heroes have cards (Soul of the Forest, Soul of the Murloc) that make a wide board "sticky", meaning an effect that destroys all your minions will not actually leave your side of the battlefield empty because replacement minions stick around. Paladin cards have no way to make wide board sticky. This is an intentional weakness for the hero.
The Paladin cards include four to clear an opponent's wide board (Equality, Shrink Ray, Consecration, and Avenging Wrath). Some decks combine these with the neutral minion Wild Pyromancer to increase their potency.
Some other heroes have minions (Timber Wolf, Tundra Rhino) or spells (Savage Roar, Bloodlust) that beneficially affect all the minions on your side of the battlefield. Paladin cards have no way to empower all your minions. However, this has been a feature of Paladin cards in the past and might return in a future expansion.
The only way Hearthstone cards allow you to act on your opponents turn is with secrets. The Paladin cards include some really great secrets.
Three Paladin cards provide a surprise burst on your turn without needing a card combination (Blessing of Might, Blessing of Kings, Truesilver Sword). Most decks include one of these to allow the player to punish the opponent for acting too greedy.
Section Two: Tempo from Secrets
Most Paladin decks include secrets. These serve two purposes.
First, they ensure that player survives the early game. This is especially true if combined with Commander Rhyssa.
Second, the secrets provide the type of efficiency called "tempo". Mysterious Blade and the neutral minion Sunreaver Spy both provide a lot of value for only two mana. Early in the game, while many secrets are still in the deck, Prismatic Lens will often makes a big minion very cheap to play. Later in the game Bellringer Sentry helps bring remaining secrets out of the deck so important minions are drawn sooner.
A common selection of secrets that promotes early game survivability and middle game tempo is: Autodefense Matrix, Hidden Wisdom, two copies of Never Surrender, Noble Sacrifice, and two copies of Redemption.
Section Three: Deck Archetypes
Secret Paladin
This deck archetype includes more secrets, Secretkeeper, Masked Contender, and Leeroy Jenkins. If you own Subject 9 that card adds extra oomph. The goal is to use the tempo created by secrets to wear down the opponent, and then use Leeroy Jenkins to finish the game.
The Magic Carpet variant includes the neutral minion Magic Carpet along with the 1-cost minions Argent Squire, Crystallizer, Mecharoo, and Glow-Tron. It tends to be weaker than the meta version of Secret Paladin, but more fun to play.
Mech Paladin
This deck archetype builds up three big mechs, and then brings them back with
Kangor's Endless Army. That goal is simple enough to be achievable, and powerful enough to win the game.
The Small Mech variant focuses on small, magnetic minions like Glow-Tron, Skaterbot, and Bronze Gatekeeper, enhanced by Call to Adventure and Glowstone Technician. This variant is one of the few Paladin deck archetypes that include few or no secrets, instead relying on its small minions to survive the early game.
The Jepetto variant focuses on three minions whose effectiveness does not depend on their attack or health values: Mechanical Whelp, Mechano-Egg, and Faceless Manipulator. The neutral minion Jepetto Joybuzz is used to draw these early.
The Fast Budget variant does not use Kangor's Endless Army. Instead it works like a less effective Bomb Hunter, with a focus on quick damage by including Explodinator and Replicating Menace and attaching magnetic mechs to a wider board. It is the weakest mech variant, but fun for players who do not own Kangor's Endless Army.
Big Spell Paladin
This deck archetype uses five big spells (two copies of Avenging Wrath, two copies of A New Challenger, and one copy of Lay on Hands) in combination with Spirit of the Tiger to rule the late game. The spells are so strong that the bonus creation of big minions will surely overwhelm the opponent.
Things get even better when Archmage Vargoth replicates those spells and bonus minions!
The neutral minion Sunreaver Warmage is included for mid-game tempo.
Big Minion Paladin
Include whichever huge minions you own and enjoy.
To some extent Big Minion Paladin can be blended with other Paladin deck archetypes. Have fun experimenting!
One Turn Kill Paladin
The deck's second copies of Baleful Banker and Holy Wrath can repeat the combination for an additional 25 damage against opponents with a lot of armor.
The Nomi variant includes Chef Nomi as an alternate win condition. This allows Shirvallah to be used in the middle of the game if needed, which can really help when the opponent has a very aggressive deck.
Either version may include the spells Time Out and/or Rebuke to help survive until victory happens.
Immortal Paladin
This deck archetype uses Crystology, Call to Adventure, and Witchwood Piper to draw the card Immortal Prelate. That minion is buffed, used until it dies, and then returns with its buffs. It grows throughout the game until the opponent is worn down. If you own Da Undatakah that card adds extra oomph.
The Recurring Villain variant adds Recurring Villain as a second returning minion to buff.
Both versions can use either secrets or small mechs to survive the early game.
Dragon Paladin
UPDATE: June 2019 had game development news about the intended flavor of all nine hero classes. It says:
Paladins are great champions who support their minions with buffs, healing, and divine shields; however, they are not afraid to get their hands dirty when the time comes. They are methodical, controlling the battlefield through debuffs and focused attacks instead of destructive spells. Strength and persistence are the keys to a Paladin’s victory.
Focuses on and excels at: minion swarms, minion buffs and debuffs, healing, divine shield, secrets
Limitated functionality with: cost reduction
Struggles to do: direct damage spells, destroying big minions