Hearthpwn

I really dislike cards that can be played for free under certain circumstances because it creates this massiv turn that are very hard to counter, especially in the early game. 

In this case one needs to take into account that spells at 5 mana or higher tend to be very powerful on their own (like Spreading Plague, Ultimate Infestation, Nourish, Flamestrike, Blizzard). A complementary 4/4 (or worst case even 2 of them) is just too much value in my opinion.

This might have to be the replacement for Corridor Creeper's spot in Tempo Mage.

I'm pretty sure it doesn't since the cost of Sprint becomes 4 instead of 7.

I've tried cards interactions like Inkmaster Solia with cards like Medivh, the Guardian and Arcane Artificer and the cost of the cards are considered to be 0.

And thus the card Atiesh will summon a 0-cost Minion and Arcane Articer will give no armor. By the same ruling Arcane Tyrant will not reduce its cost since the cost of the spell you cast is not 5 or more.

that's not a priest spell though - it's a mage spell.

Would the auto-casted Scroll of Wonder proc this guy?

No, it didn't on the reveal stream. They don't synergize because they're not cast by YOU exactly. They cast themselves.

This might actually help make DOOM! playable, because now, instead of spending your entire turn destroying everything and overfilling your hand, you can destroy everything, fill your hand, and drop down one or two 4/4s onto an uncontested board.

That being said, running two of them in your deck to aid DOOM! isn't optimal, but thankfully, warlocks also have Felfire Potion, Twisting Nether, Bane of Doom and Siphon Soul, not to mention all the seals from Rin, the First Disciple, the 5 and 10 mana Kazakus Potions, a bunch of spells that you can discover with Kabal Courier.

So, TL;DR, I think I'm going to give this a shot in warlock and have some fun with it!

brother of Cabalist's Tom

I thing , calling Elemental to Arcane beings are a bit weird. Due to they not actually. 

They're essentially mana elementals, instead of being made of fire or water or any other substance, they're made up of arcane energy.

Because it's like Kun, another card to empty your hand after nourish/UI/spreeding plage and keep your tempo going. It will see play.

Because a 0 mana 4/4 in Hearthstone is good. I really don't see your point, seems like you need to learn a basic principle in Hearthstone which is tempo. Casting a 5+ mana spells is bad, playing one or maybe even two 0 mana 4/4s is great because it helps salvage some of the tempo loss from casting that spell.

I think Tempo Mage is just about the last deck where this card will see play. It will be in every slow deck with a ton of draw, such as Druids with UI.

If its sees play at all it will most likely be in Druid, with UI, Nourish and Plague, Druid has enough hand refill to warrant this card.

Missing the best card. 

Ultimate Infestation. In ideal case it will be draw 5, deal 5, 5 armor, summon 5/5 and 2 4/4

This also helps the overdraw problem with UI a lot, if you have 10 cards in hand afterwards but can play one of these for 0, it's a pretty big advantage. Also, a free 4/4 minion is always pretty impactful, especially if you get it out on turn 4ish after ramping into Nourish or alongside another medium threat like a 5/5 from UI. It might not be better than a Jade Golem, but if this doesn't make the meta in K&C, I have a feeling it'll be played a lot in the first set of next year.

Nice card  to play after a big boardclear.

Conversely, you can pull off its requirement proactively and not wait for the opponent to hit you. Also you likely have more cards that can trigger it.

psychic scream