Mulligans
Combo Mulligans
Tamsin will be the most difficult combo piece to find, since the others are spells and can be easily grabbed by Hulbreaker.
Only keep if Expired Merchant and Hand of Gul'dan get offered together.
Warlock
Win condition
Play Tamsin Roame. Play Wicked Shipment that has been traded twice. Play Tamsin's Phylactery dicovering the effect from Kobold Sandtrooper. Repeat this with the free copy from Tamsin Roame. Play Plague of Flames dealing 42 damage to the enemy hero.
4 card combo with the prerequisites of trading a Wicked Shipment twice and playing one Kobold Sandtrooper.
At max 9 mana, but usually will be discounted by Runed Mithril Rod during the game.
Strategy
Like most combo decks, draw and survive.
Draw
Dreadlich TamsinHullbreaker *2
This can draw you Wicked Shipment *2, Plague of Flames *1, Tamsin's Phylactery *1, Hand of Gul'dan *1, a Soul Fragment or a Fel Rift. Sometimes you might take 6 damage from drawing Hand of Gul’dan, if you have a hard time surviving you probably cut the Expired Merchant + Hand of Gul'dan combo.
Witchwood Piper *2
Not really for the targeted draw, more just for cycle. Also a demon to go with Man'ari Mosher.
Expired Merchant *1 and Hand of Gul'dan *1
Might not be worth it tbh. If you happen to have them both in hand, 2 mana draw 3 is pretty big. You could just never touch the 2 copies that return to your hand since your combo only needs 4 cards. You should have the handspace. If the Hand of Gul'dan cost gets reduced by Runed Mithril Rod you could always play a 4 mana draw 3.
Survive
Demons
Midway Maniac Man'ari Mosher Hullbreaker Witchwood Piper Fel Rift
Some parts of your draw engine are already demons. Adding Man'ari Mosher will give you some extra hitpoints to survive. Midway Maniac is a cheap 5 health taunt that could help you gain an extra turn.
Life gain
Blood Shard Bristleback Luckysoul Hoarder Man'ari Mosher Zilliax Dreadlich Tamsin
Tech cards
Acidic Swamp Ooze *1
Mostly against Lightforged Cariel, yet other weapons might be prevalent.
Irondeep Trogg *2
I might be overrating this card. I wanted an extra 1 drop to establish early board control and in a spell heavy meta, this seems like a great pick. Playing it on turn 1 gives you an edge on aggro decks that want to coin out a bunch of stuff from the start.
GL HF