Hearthpwn

1. Cycle through your deck, work on quest

Use small && easy to play deathrattle minions that draw you cards and help with quest. Hold off with playing non-draw deathrattles unless you have to - the worst situation that can happen - you run out of draw... Think what you will resurrect with Twilight's Call

there are also 2 x Novice Engineer to accelerate card draw and fill the gaps...

While you are at this you will hopefully get some extra Coins from Gilded Gargoyle depending on your draws/resurrects... Do not hesitate to use some of those if you need to, for example to get earlier Psychic Scream or to avoid overdraw, after all you need just one for the combo and 2 if you consider nuking deck with one Galvanizer in it.

2. Stall your opponent turning their existence into a painful nightmare

Spirit Lash, Bloodmage Thalnos + Spirit Lash

Doomsayer - 2 mana board clear/heal for 7 which is always good for such kind of deck

Glacial Shard - helps to reduce damage you take for 1 turn, has decent synergy with Doomsayer

Ironbeak Owl - sometimes and probably -often- once boomsday fully lands silence in an absolute answer. There are a lot of buff oriented decks and if magnetic gonna be a thing it's better to run 2 of those. Considered running Shadowreaper Anduin instead but most of the time it's a dead card and a problem to get rid off when u getting closer to the combo...

Psychic Scream - this one is extremely powerful because it also turns your opponent's deck into trash and totally ruins all those even/odd/spell only decks... If you expect your opponent to flood board with a lot of small minions/buffs, discover at least one extra with Shadow Visions. Then watch them top-deck their 1/1 while u march towards end of your deck

Amara, Warden of Hope - your quest reward and your ticket to life. Deck nature allows you to finish the quest as early as turn 6 stopping aggro onslaught and giving you board tempo. In some games you can be more greedy and play Amara, Warden of Hope together with Zola the Gorgon - this most certainly will buy you a lot of extra time

3. Nuke the remnants of your deck

Once you got at least 3 mana reduction with Galvanizer / Coin, drew one Shadow Word: Death and finished the quest there is almost no purpose in having those cards

4. Plan your card usage ahead

You run only cheap non combo cards(3 or lower mana) with a few notable exceptions - 2 x Psychic Scream and 1 x Hemet, Jungle Hunter. Those are extremely powerful, high impact cards that will allow you to stay alive over the game or jump straight to your OTK Combo. Take care when to use those, because in order to go with combo you should get rid of all cards in hand except those needed for the combo while staying alive... 40 HP helps just for a while...

This is probably the most challenging aspect of this deck - you need to know your deck and your opponent's deck very well. For example there could be an issue - you got rid of every card except an extra copy of Shadow Word: Death -  do not hesitate to kill your own minions with it if you really have to

5. Combo

Once your deck is empty and you have no extra cards in your hand

Mecha'thun + (1-3) Coin + Shadow Word: Death

Caboom!

If you liked the deck, please, +1. If you have ideas/suggestions - leave a comment, let's improve ;)

Edit: I've tested the deck shell on current standard ladder and got pretty good results vs control and mid-range decks and mixed vs aggro(shell I tested is weaker than this deck in quest completion)... Seems like this will be strong combo deck