Cards that can do non-combat damage to multiple targets (either multiple targets at once,
or repeated damage over two or more turns (when you're able to target different people each turn))

CARDS THAT DO ONLY NCD TO HEROES (but not allies) ARE EXCLUDED, because who cares about hero NCD?




Adept Breton (Alliance Ally <2>)
    Pay 3, activate. Adept Breton deals 1 arcane damage to each opposing hero and ally.

Melgwy Pingzot (Alliance Ally <2>)
    5, [Activate] --> Melgwy Pingzot deals 5 fire damage to target hero or ally.

Lt. Commander Dudefella (Alliance ally <3>)
    Pay 1, [Activate] --> Dudefella deals 1 frost damage to target hero or ally. A character dealt damage this way can't attack this turn.

Tim (Alliance ally <3>)
    Elusive; [Activate] --> Tim deals 1 arcane damage to target hero or ally.

Primalist Naseth (Alliance Ally <6>)
    [Activate] --> Primalist Naseth deals 4 nature damage to target hero or ally and heals 4 damage from another target hero or ally.

Acolyte Demia (Alliance Ally <6>)   max 6 damage
    Pay 1, Put 1 damage on Acolyte Demia -->  Demia deals 1 shadow damage to target hero or ally. Use only on your turn.



Elithys Firestorm (Horde ally <2>)
    When Elithys Firestorm attacks, she deals 1 fire damage to each other hero and ally.
        (though the fact that she needs to survive to attack someone, and that she's only 2hp means she
        won't survive long in the mid/late game, but she would be pretty valuable as a second-turn
        card, or in combination with "Lust for Battle")

Dark Cleric Ismantal (Horde ally <3>)
    Pay 4 --> Dark Cleric Ismantal deals 1 shadow damage to target hero or ally. That character's controller discards a card for each damage dealt. Use only on your turn.

Arnold Flem (Horde ally <4>)
    When Arnold Flem is destroyed, he deals 1 fire damage to each opposing hero and ally.

Hierophant Caydiem (Horde ally <4>)
    Pay 3 --> Hierophant Caydiem deals 1 nature damage to target hero or ally and heals 1 damage from another target hero or ally.

Panax the Unstable (Horde ally <5>)
    Pay X, Destroy Panax --> Panax deals X arcane damage to each ally.

Lokholar the Ice Lord (Horde ally <14>)
    At the start of each opponent's turn, Lokholar deals 2 frost damage to each hero and ally in that player's party. A character dealt damage this way can't attack this turn.



Grimdron (Warlock ally <1>)
    Elusive; 1, [Activate] --> Grimdoom deals 1 fire damage to target hero or ally.

Infernal (Warlock ally <6>)
    At the start of your turn, discard a card, or target opponent gains control of Infernal.; At the end of your turn, Infernal deals 1 fire damage to each opposing hero and ally.
        (wow...  not only does damage to lots of people at once, but also does it every turn)



Helmet of Ten Storms (Shaman armor <4>)
    Pay 2, [Activate] --> Your hero deals 1 nature damage to target hero or ally and heals 1 damage from target hero or ally.; When you play a Shaman ability, ready Helmet of Ten Storms.



Helm of Fire (armor <3>)
    Pay 5, Exhaust your hero --> Your hero deals 3 fire damage to target hero or ally.

Netherwind Crown (Mage armor <3>)       ($16!!!)
    Pay 1, [Activate] --> Your hero deals 1 arcane damage to target ally.; When you play a Mage ability, ready a Netherwind Crown.

Skullflame Shield (armor <6>)
    When your hero defends, it deals 1 fire damage to each opposing hero and ally.
        (in practice, it would never kill anything because the other person simply wouldn't attack the hero)
        Good in combination with "Stalwart Protector" (warrior)
        Good in combination with "Vigilance" (warrior)
        Good in combination with "Rockbiter Weapon" (shaman)
        Good in combination with "Sacred Duty" (paladin)
        Good in combination with "Undaunted Defense" (paladin)
    
Flame Wrath (weapon <4>)
    When your hero deals combat damage with Flame Wrath, your hero deals 1 fire damage to each opposing hero and ally.

Rod of the Ogre Magi (weapon <4>)
    Pay 2, [Activate], Exhaust your hero --> Your hero deals 1 damage to target hero or ally.

Thunderfury, Blessed Blade of the Windseeker (weapon <9>)
    When you strike with Thunderfury, choose up to five heroes and/or allies. Your hero deals 5, 4, 3, 2, and 1 nature damage to them, respectively.



Blade Furry (rogue ability, <4>)
    Ongoing: When your hero deals combat damage with a weapon to an ally, you may have your hero deal that much melee damage to another target hero or ally.




=== Cards that sort of meet the criteria ===
            (or they fully meet it, but still seem rather limited, or pretty difficult to actually deal non-combat damage)

Mezzik Darkspark (Alliance Ally <1>) 
    [Activate], Destroy an ally in your party --> Mezzik Darkspark deals X shadow damage to target hero or ally, where X is the ATK of the destroyed ally.

Wilba (Alliance ally <4>)
    When a Spider in your party deals combat damage to an ally, destroy that ally.; 3 --> Put a unique Spider ally token named Charlotte with 1 ATK and 1 health into play.

Watcher Mal'wi (Horde ally <4>)
    When an opposing ally enters play, Watcher Mal'wi deals 1 ranged damage to it.
        (never kills anything in practice...  because the other play knows it's there, they simply don't put any card in play that has only one health)