This is my first submission. A redeemed Nathrezim who gives synergy with self-damage Warlock and unlocks potential for Rastakhan Paladin.

Radiant Conjurer is a card that supports Paladin and Shaman through the use of summoning minions through Hero Powers, which in itself synergizes with Even Paladin and Even Shaman decks and support for Silver Hand Recruits and Totems.

Break down the barriers between the cosmos and dominate with spells from beyond!

Freeze is mage focused, Lifesteal is warlock focused (also mage in the past) and i thought twinspell could allow for monstrous value for both classes.

On some days even they can't "let it go".

I combined the discarding effects of Warlocks with the Big Spell Mage kind of gameplay (like Dragon's Fury) to create a card that doesn't fit either of the classes well :D

Okay, sometimes you might need an early AoE when playing Mage so you might be prepared to give up two cards for it to happen. And Hand of Gul'dan does have amazing synergy with the card (but the Zoolock playstyle does not).

Pick your poison, but remember, it's the dose that makes a poison!

IMPORTANT !

"Gain an empty Mana Crystal" is a part of both options. To fit in the card text space I could not add "Gain an empty Mana Crystal" twice, so I found seperating this sentence from the choose one options to be the best way to do it. I'm sure most of the understood it anyway :).

Haven't done one of these in a while, but I was inspired by the art, which was a Druid like figure surrounded by what I imagined to be Hellfire.  Since one of the effects is basically Hellfire with a body I increased the cost to 5 mana.

Because the card text doesn't say "Give your other  minions..." then the card would buff itself if you choose the buff option, essentially making it a 5 mana 4/5 that gives +1/+1 to your other minions.

If you are able to play it with combined effects, the buff happens first so any of your minions at 3 health would survive the board clear effect after buffing to 4 health.

Support for Deathrattle Hunter and Deathrattle Rogue.

Originally I thinked to create a card with represented the explosive turns that both classes can make with his insane draw Power, giving extra damage for each card drawed in the turn. But i remembered that Myra's Unstable Element exists, and not looks right this card can't target face. So I thinked, well, both classes can cast a bunch of stuff in a single turn and can sometimes give a bunch os damage in the process, burning all of his resources. The card fell right then, a card like [Hearthstone Card (Edward Van Cleef) Not Found] and Altruis the Outcast, paying off his building around with you in all in mode.

Paladin gets a choose one effect, while druid gets some stats setting that paladin normally gets, such as Humility and Keeper of Uldaman.  The effect is not particularly efficient but very versatile, either by buffing a friendly minion or weakening an enemy one in two ways.

There's halitosis, and then there's "I breathed on your axe and now it's poisonous."

Gurtogg is a boss from Black Temple - the same dungeon that gave us the Reliquary of Souls, Teron Gorefiend and Akama's Shade form, as well as encounters with Illidan Stormrage and Maiev Shadowsong. He is part of Illidan's fel orc forces and is renowned for his corrosive fel breath. 

I thought Warrior and DH made perfect sense for Gurtogg, and weapon synergy was the obvious choice for overlap. No one outside Rogue has ever had Poisonous weapons, but I thought Gurtogg's corrosive attacks made for a good excuse to spread the sweet, toxic love.

Artwork by Brian Dugan

He grants this powerful ability by chanting the melodic incantation: MRGLRGLRG.

-Professor Slate's favorite lighter-

This card helps Warlock's self-damage synergies and Mage's Spell Damage synergies (or could even just be played on turn 3 with Khadgar for a strong tempo turn). I thought it would be interesting to try and create a self-damaging card where you want to deal more damage to yourself. Of course, it can also just be played as a less-consistent (but less damage) Flame Imp.

Both classes have an arsenal for card draw, mostly fitting into aggro style decks. Low HP for counterplay.

Pretty Aggro card. I’d add “random” to text, but alas, ugly text... could be used either as cheap draw or cheap ramp (should be more useful in Warlock, since they don’t have ramp and can refill hand more easily + discard synergy) 

Scholomance Academy needed at least one mad professor. As a visiting professor from Shadowfang Keep, Lord Walden ensures something crazy will happen and that someone will die (which pleases Kel'Thuzad).

Note: Like Yogg-Saron, he can (and likely will) kill himself with his own Battlecry.

The Spectral Researcher is a mob in Scholomance (WoW).

The card has stealth of rogue and the copying of your opponent's card of priest. Great card gaining when your opponent can't deal aoe or random damage, but easily removed if they do. But can also be used to bait aoe removal, because it has great potential control v control match-ups or in a mill deck.

For the people thinking that a permanent stealthed minion is controversial and shouldn't exist: I think that could be said about a lot of cards that were released over the last few expansions (Scholomance in particular), and those seem to be fitting in just fine.

Despite the outfit Shadow Hunters are the spiritual leaders of many troll tribes.

Murlocs ride on Turtles, Silverhand Recurits carry Wolpertingers. AND CHARGE!

Art by Aron Gabor

There can be no Neutrality in a revolution! Edwin's forces are mobilizing, and it's only a matter of time before they rise up and take what's theirs.

Playing off the original Edwin VanCleef, Edwin the Revolutionary is a 3/2/2 with Combo, but also the No-Neutral clause from the Paladin. I see this working out in two different ways: for the Paladin, he already has various No-Neutral cards he can play with and benefit from; with the Rogue, she can bounce Edwin multiple times with Shadowstep to play a sort of new-age Prince Keleseth setup.

They always tried to be the coolest guys in their school.

Hunter's and Rogue's Secrets are easy to be triggered,making it card for other cards related to Secrets to achieve some combo.Zoey enables them to play many Secrets in one turn while keeping them to achieve combo.Your opponent can have a chance to deal with them as well.

She claims to have discovered the Secrets of the world,however,nothing can prove that.

A tricky sleight of hand master who uses dark magic and misdirection to distract your opponent and mess with their cards. It fits rogue because of the sneaky and tricky aspect of it, and it fits warlock because of all of their disruption tools (Gnomeferatu, Chaos Gazer, Demonic Project, etc). 

You can use this with bounce tools and such to discard your opponents entire hand one at a time, but I don't think it is anything to worry about. With the time and effort you would have to put into discard your opponent's entire hand you could just play Howlfiend and Treachery, or Coldlight Oracle and bounce stuff.

'...was a jolly happy place.
Where the trees stand tall and the Druids sleep
While Rogues stab you in the face.'

Paladin and Druid are famous for their buffs. Paladin usually buffs single targets, while Druid is better at AoE buffs, but each class has both of these. Note: The second option is meant to buff itself.

"He really knows how to take a college party to the next level (or two)". Sneaky Shifter is a Rogue/Shaman minion that brings the Evolve mechanic from Shaman and combos it with... well, Combo. Works well with current Evolve Shaman decks while also being a build-around for Evolve Rogue decks, or just to buff Lackeys in Galakrond Rogue.

"You feel the thunder coursing through your veins! It's exhilarating! Just note the side-effects of: Heart Failure, Corrupted Blood, and Spellshock."

Warriors like big minions - Druids like big minions. Just imagine if Rattlegore or a Marsh Hydra tried to give you a big hug!

Both classes have a fondness for big minions, and both have a preference for minions that have effects when they attack or are fast in some way. Bear Hug lets warriors and druids leverage that playstyle even further by triggering a valueable "on attack" effect, or simply giving their rush minion "windfury" for this turn.

This fox is a rare bread that lives in the magical land of Surumar. Wildlife there is often infused with arcane energies, balancing the magic of mages and druids. 

“The Headmaster REALLY doesn’t want you wandering the halls.”

After various designs, I settled on an idea from a previous custom class of mine. After your Secrets are revealed, you can spend two mana as a Hunter or Rogue to recast them! Your opponent knows what they (or some of them) are, but now has to fight through them again! 

A fusion of Priests healing and Hunters Beast synergy. The hunter aspect of this is obvious, using it to either buff beasts, or heal and buff a Rushing beast. Priest might need to look a little harder, but this could be used in tandem with Bad Luck Albatross, or even look to use something like Spitting Camel, Escaped Manasaber or Hippogryph, all minions with a larger health pool, and in the case of Hippogryph, Rush as well.

In wild this has a few more applications, with Dire Mole and Plated Beetle among others.

A minion that combines some of the core mechanics and flavors of both classes. You hit him, he vanishes then returns with newfound protection for another round.