Hearthpwn

Quite the finisher for Control Warrior, all you need to do is armor up like crazy, stick it on an existing minion, or discount a stonetusk boar. 

One Turn kill: Use Thaurissian on her and 5 secrets first.

Flavor text: "I was facing dangers far worse than that little twerp of a demon when your great-grandparents were infants."

How to OTK:

1. Fill the board with cheap minions. Forbidden Ritual, Wisp, Murloc Tinyfin, Voidwalker etc.

2. Drop a Flesheating Ghoul for extra damage.

3. Cast this spell and go face.

Basically this legendary is a beefed up Pyromancer. While most of its spells work with Mage, Warlock and Shaman have a spell as well that this can be used with.

A beautiful wombo-combo featuring not less than brand new Pantry Spiders, rock solid Arcanosmith and an even better Purify!!!

Combo:

Turn 0: Emperor Thaurissan

Turn 1: Northshire Cleric (0) - Northshire Cleric (0) - Pantry Spider (2) - Pantry Spider (2) - Arcanosmith (3) - Purify 2 (1) targeting NC 1 - Wild Pyromancer (1) - Purify 2 (1) targeting NC 2 - Circle of Healing (0) - Circle of Healing (0)

10 mana. 36+ cards drawn

Disclaimer: there must be two minions slots on the opponent's part of the board.

Ten cards are used, hence Emperor Thaurissan is to discount all mana-intensive cards and the player is to draw (three attempts) the last 0 mana card. However, even with a 9-card combo the opponent draws 28+ cards, which is enough for a Wow! emote.

It came between this and "Deathrattle: If this minion is summoned by N'Zoth, turn it into a 30/30 Deathwinger, Harbinger of Destruction" but this version felt more balanced.

Edit: Image didn't properly attach

Can be used for an OTK, or can be used throughout the match to reduce the cost of spells (so you're not stuck with one strategy). Lots of ways to deal massive damage, but one example would be:
Witching Hour + Witching Hour +Frostbolt +Frostbolt + Ice Lance + Ice Lance +Fireball = 9 mana for 30 damage, and this is without Emperor Thaurissan.

A bit more reliable I'd say.

Combo : 

played before: Tundra Rhino +Stranglethorn Tiger x2 + Animal Companion x2 +Timber Wolf

turn 10: loque'nahak with 32 to 40 damage (depends if you summon 0 or 2 Leokks), but it works like Anyfin Can Happen so enemy beasts could ruin the otk, also the beast only last for the turn so it's not that broken.

and for the animation it could be like spiritual minions with a blue glow.

PD: sorry for my poor english :p

Though it's not quite 30 damage, and this card probably won't count because of that, I'm happy enough with this card to post it as it is. Murloc Paladin was considered OTK, so even though this isn't "combo," it still acts like one. The maximum damage I can count is 26 damage.

Before I begin explaining it, let me just mention that Warcraft-relatable art for pirate stuff is near impossible to find. That said, given how iconic Captain Cookie was (for people who didn't play WoW, or at least not Deadmines, Captain Cookie was a Murloc-Pirate dungeon boss), and given that there's potentially-possibly-probably some similarities between this and another card, for some reason Captain Cookie and his unique race just seemed to fit.

So, how this card works is this. If you have had at least 5 pirates die while on your side of the board, a random 5 of them will be resummoned. If you have 5 or more pirates dead when you play this card, the second half of the text is triggered, and you summon an additional random 2 from that 5+ original pool of pirates.

As far as damage is concerned, the highest I can think of at 6:45am with no sleep is this:

3 Kraggs = 12 damage
2 Deckhands = 4 damage
2 Captains = 10 damage

But I think the Shady Dealer and Ship's Cannon (in wild) value, and the use of "ye," absolutely make up for it. Does it count? :)

OH WAIT IT COMBOS WITH Eviscerate FOR EXACT LETHAL IT TOTALLY COUNTS!!!

Intended Use: Let's assume that a card actually has an intended use, rather than just being an OTK tool. So this card should enable you to cycle some extra healing, draw some extra cards and make priest and overall much stronger healing class.

BUT

There is also the "abuse" opportunity, as this competition demands:
Step 1) Assemble the combo pieces in your hand: THIS (6) + Flash Heal (1) + Flash Heal (1) + Embrace the Shadows (2)
Total Cost: 10. So you could just play this at ten and deal 10 damage to whatever you want. Pyroblast (in essence).
But there's more.
Step 2) Draw Emperor Thaurissan and play him. He will be removed that turn by the opponent, but now our combo pieces are at 5/0/0/1. That costs (6) in total and leaves is with 4 empty mana crystals. Each time we play the Flash Heal, we get another Flash Heal copy from the card. That leaves us with 6 Flash Heals for 0 + 0 + 1 + 1 + 1 +1 = 4 Mana in total. So we play
- This card (5)
- Embrace the Shadows (1)
- Flash Heal * 6 FACE
- And then 2+4 Flash Heals which equal exactly 30 damage. Well played.

2x Bluegill Warrior + 2x Ocean's Calling + 2 Everyfin is Awesome for 36 dmg.

2x Grimscale Oracle + 1x Bluegill Warrior + 2x Ocean's Calling + 1x Everyfin is Awesome for 30 dmg.

1x Murloc Warleader + 1x Bluegill Warrior + 2x Ocean's Calling + 1x Everyfin is Awesome for 30 dmg.

Emperor ticks needed in all options.

Emperor Thaurissan reducing the cost of all the following: Brann Bronzebeard, Loatheb, 2x Curse of Rafaam, 2x Curse of Curses. The opponent takes 4 damage at the start of their turn and 32 more at the end. Brann + Loatheb makes all the Curses cost 12 so it's extremely unlikely they'll be able to get rid of them.

Assuming all combo pieces cost was reduced by Emperor, the combo is:

Steward of Darkshire (2) + Hand of Protection (0) on steward + Duskboar (1) + Magma Rager (2) + 2x Abusive Sergeant (0) + Divine Revenge (5) makes exactly 30 damage from empty board.

This may seem OP, but imagine paladin gathering 8 cards in his hand (emperor+combo) to pull it off.

 Also, that card would be situational bubble-removal tool like Blood Knight.

EDIT: +3 attack was way too much. Changed to +2 attack.

Combine this with Brann Bronzebeard with some Molten Giants in the deck.

When you created nice board, which can end game this turn, but your opponent is hiding behind taunts.

Assuming some magic from our good friend Emperor Thaurissan: 8-cost Malygos + 0-cost Molten Giant + 2-cost this to opponent's face (then realize you didn't even get through Control Warriors armor and concede). Little bit like Holy Wrath + Molten Giant, only more reliable. I'm not sure if I was allowed to assume a 0-cost Molten Giant but I did it anyway.

NOTE: It will deal damage equal to the full cost of the giant, 25 (+5 from Malygos), and not 0.