Mulligans
General Mulligans
Get corpses early and start spending. Only copy with fizzle when you have high value cards in hand for the long haul against control decks, extra Necrotic, Titans or key corpse spending cards. Get as much on the board as quick as possible, it quite strong as pure agro, Murloculas after Mining Casualties or crop rotation, cycle through the deck with Acolyte. You have so much value generation it doesn't matter if you get low cards, and if you do, Harth will give you a free killer hand. The plagues are useful for stopping Brann warrior, or any draw decks and good for early control if you need it, but if you can't make legendary with this, you probably need to quit Hearthstone...
My first trip to legendary with a deck I came up with myself, 14097!, at present it has no weak matches and is a bit over-tuned. I went from Diamond 5 to legendary in about 7 hours. Use fizzle for multiple necrotic explosions, extra plagues or corpse spenders, only one Vizier, no tour guides so you can fit in Helya and Down with the Ship to punish draw decks, no Miracle Salesmen so you can fit in Yogg as well. It works as control, combo, agro. It feels like you’re cheating 🙂