At first I want to say that this deck will not be a ranked deck, it's more like fun deck (we will see anyway)
How does combo work ?
It's a bit complicated. Firstly, you have to play Vereesa Windrunner (it's better to play her when you are close to end the game, so that weapon will have higher chance to survive). After you empty your deck with Arcane Shot, Goblin Prank, Oblivitron and Mecha'thun in your hand, it's time to do some magic.
Play Oblivitron. Then, attack with weapon from Veressa to gain Spell Damage +2. Kill your Oblivitron with Arcane Shot - it will summon Mecha'thun from your hand. Last thing is to play Goblin Prank on Mecha'thun and gg!
Can I survive until I combo ?
Well... it's possible. Although feel free to change cards to improve this deck (I'm not the best at deckbuilding :P). There are some draw cards (Novice Engineer, Cult Master or Witchwood Piper) as well as cards that allow you to control the board (somehow) like Marked Shot or Springpaw with Hunter's Mark.
I will probably expand this guide when Rise of Shadows will be released. Until then, fell free to leave feedback :)