Hearthpwn

Unity: is considered all tribes.

Explanation: the card counts as a Dragon, Beast, Demon, Murloc,  Mech etc. etc. and therefore interacts for instance with cards like: Timber Wolf, Old Murk-Eye, Gorillabot A-3, Mal'Ganis, Dragon Consort. This makes it possible to create fun decks: Paladin Murloc Dragon deck, Pirate Beast Hunter deck, Totem Mech Shaman deck. etc etc A simple but fun keyword!

Quest is used to send minions away from the battlefield and have them return on your following turn with a Reward (referred to as "turning in a Quest").

Rewards vary and are dropped randomly based on the given Quest but are always a minion, spell or weapon card which is added to the players hand when the minion returns.

Chalice Chaser is always looking for more party members to help find the next great treasure.

Lady of Chains, a member of The Chains Assassin Syndicate, is always recruiting new members to execute their latest contract and compelling them to continue their quest chain until they succeed or die.

Evangelista is an  unholy prophet on a mission from the Old Gods to make your mission her mission too.

The Quest ability is removed before the minion returns to the battlefield. Their return is counted as a fresh "summon" but not as "played" from the hand. Some Quest effects can target opponents' minions.

Reward is not a standalone keyword for this challenge but was included for clarity. Reward does not produce unique tokens, only cards from the format card pool.

(minor text fixes)

Since I am an extremely lazy person, I'll post my mechanic and three cards from my Twisted Timelines set:

A card with Delay enters the battlefield (if a minion or weapon) or is cast (if a spell) after the number beside the Delay keyword.

A minion or weapon will still trigger its battlecry after it enters play with delay. A card that is waiting to enter play with delay is referred as Delayed. Some cards interact with Delayed cards.

The target of the delayed card is chosen after the Delay effect. If there is no target left, the card is cast anyway. A minion won't trigger its targeted battlecry and a spell will count as if it was cast but have no effect.

Muradin Adventure cards:

The keyword I came up with for this week is pretty simple, so i came up with some more sophisticated cards.

First, the keyword itself.

Pretty simple, huh? (Originally it was named SMOrc, but someone has taken the name, so my entry will be less meme-y :c )

To clarify: It doesn't matter how many of your minions have attacked, this can occur once per turn, even on the turn the card with Surge has entered play. 

I was inspired by the Duel Masters' effect called Turbo Rush.  

                                                                           Patches the Pirate

As you can see, the effect can also have some drawbacks, so you gotta decide whether to go face or not. I hope you'll like my invention. :D

Unpredictable: Gives the card text a 50% chance of occurring.

I thought this would be very interesting for traps, making it harder to identify what the trap in play is. It could also be used outside of traps as well I suppose though, similar to the ogre cards. 

Edited: Image size (to fit into one row) 

Ambush: Do X if summoned not directly from hand.

The opposite of Battlecry, will work with every effect that places the minion directly on the battlefield, for example Ancestor's Call, Barnes, or any Deathrattle effects (Piloted Shredder, Moat Lurker.

Kindly： if you play a card with keyword 'kindly',put it into your opponent's  collection from yours after this game.

Balance (X): You get the effect if you play this card when you have exactly (X) mana left.

This requires the player to think about the most optimal way of playing his/her cards to get the maximum out of them.

Arcane Prophet is a decent 3 drop but if you play him on turn 4 you might be able to immediately follow it up with a 1 mana damage spell. If you need the Spell Power later than you will have to spend mana until you have exactly 4 left when you play it.

Last Light would allow for some nail biter combo decks. You can decide if you would rather draw 4 and try winning with 8 mana this turn and 10 on your next, or you might think you have a better chance if you play it when you have 6 mana left and get two more cards, but only 4 mana this turn and 10 on the next.

Lord of Carnage is more straight forward. A 5 mana 5/5 Demon, or if you play him with exactly 9 mana left then he is a 5 mana 9/9.

Channel (X)

Does something at the start of every turn for the cost of (X). If you don't have enough mana to activate the channeling effect, the channeling is stopped, and does not activate on subsequent turns.

First time i try to create some cards... Let's see if i can make it ( sorry in advance for my english )

I hope this is understandable... I hesitated a long time between protecting lower health or attack minions ( both would have been too strong i think ). But i seemed more logic to me to protect lower attack ones.

At first it seems quite like taunt, but it creates lots of new ways to keep some minions on the board, as there is also a lot of ways to play around it. 

Indignant is what could be a "classic" buff to turn a normal minion into an effective protector.

Okay, this one seems not so efficient, but with a good use of his deathrattle ( and, maybe, the RNG god with you ), you could gain a huge board control by turning a great minion into a protector.

And finally, some fun and efficiency with this legendary one !

This is THE protector ! Hope you like it. Wanted to have some fun making my first cards.

I didn't make any basic Protector cards, because i wanted to explore a bit what the mechanic could give with some combo. Grundalf seems very strong to me, but can also be defeated quite easily or even at the advantage of the opponent ( his death triggering an opponent deathrattle... and more). The same goes for the Keeper of Legacy...

Sort of like returning a minion to your hand and replaying it without paying its mana cost and without the battlecry. Kind of an undo-silence effect (kinda.) Removes buffs but not deathrattles taunt and divine shield, also heals if the minion is damaged. Also gives a minion divine shield if they lost it. 

Some comments if you want:

Condition: Depending on what you have done in the game, This minion will activate.

List of Unique hero powers:

Surrogate is a variation on taunt. The most direct parallel to draw is that it's a keyword form for Bolf Ramshield's effect, but not constrained only to one minion, or only to your hero and the minion. When a minion is protected by another with Surrogate, attacking the protected minion will deal damage to the Surrogate, but will use the attacked minion's attack as retaliation. Surrogate minions can be targeted by transformation or destruction effects like Polymorph and Shadow Word: Death as normal.

Ruins Guardian: Protection for your key minions, but without much bite of its own. Be sure that one of the minions it's covering doesn't have zero attack, or the Guardian can be chipped away at for free, much like Bolf can. Doesn't protect your hero any. Could be handy in Priest.

Bind Soul: Sacrifice your minion's attack for health and make it your meat(?) shield. Meant for the controlling Warlock who needs to buy time and force a friendly minion to protect them, taunt or not. However, since your hero doesn't have any attack, the minion often will die without fighting back. Possibly useful with minions with powerful end of turn effects, avoiding attack based removal, or just to block some of Freeze Mage's burn headed towards your face.

Recalled Goblin Bodyguard: A way to close out games for the 5000 armor Warrior. Any damage this minion takes, goes to your face instead. Perhaps too powerful, especially if taunt is given to it, but I feel 8+ mana cards should be ways to end the match. Be aware of spells that only damage minions, such as Flame Lance or Elemental Destruction, as they can now technically be cast on your hero. Like all Surrogate effects, is vulnerable to transformation, silence, or direct destruction removal. Be careful of having two on the board, as AOE spells like Consecration would deal triple damage to your hero.

Gnomish Spy: An decently stated minion which can help give you an idea of what type of deck your opponent is playing.

Risk Assessment: Allows you to cycle a card whilst giving you more information about your opponents deck.

Orgrimmar General: A slightly below average midgame taunt that helps you determine what late game finisher your opponent is using, If you already know what it is (e.g. C'Thun doesn't really make his presence a secret) it also lets you know if your opponent has drawn their finisher or not. 

In general the keyword is designed to A) help you work out what deck you're up against and B) In situations where you know your opponents deck list (like tournaments) it also tells you information about whats NOT in their hand, narrowing down what counter-plays they might try and make and letting you be more confident in your decisions. 

EDIT: Adjusted the card size so all three fit on one row (instead of 2)