When to Mulligan: You should have at least two lands and two rogues in your starting hand. Every combination of two rogues can pretty consistently get 7 or 8 cards in the graveyard by turn 4 or 5, which turns on their abilities, Vantress Gargoyle, and Into the Story.

How to Sideboard:

Replace Vantress Gargoyle and Merfolk Windrobber with Cling to Dust and Grafdigger's Cage against graveyard based decks.

Replace Feed the Swarm with Cling to Dust against burn.

Replace Feed the Swarm with Languish against Stompy decks or RDW.

Replace Call of the Death-Dweller with Inquisition of Kozilek against combo decks.

Feed the Swarm is for Leyline of the Void or Rest in Peace.

Upgrades: 

Assassin's Trophy over Feed the Swarm

Breeeding Pool over Island

Verdant Catacombs over Clearwater Pathway

Misty Rainforest over Shipwreck Marsh

1 Watery Grave over 1 Underground River

1 Scalding Tarn over 1 Underground River

Thoughtseize over Inquisition of Kozilek.

Damnation over Languish.

Because this deck hasn't been played in any format since Zendikar Rising was in Standard, I feel a need to explain it. Rogues give you the small evasive creatures that control decks often run, while enabling Drown in the Loch, which is basically an unconditional 2 mana counterspell or kill spell in this deck. In addition Into the Story is one of the best draw engines, especially because turn 4 is usually where you need to refill your hand, so casting this on curve feels really good. This deck does not have a big bomb, although feel free to slot in Hullbreaker Horror for Call of the Death-Dweller or Vantress Gargoyle if you feel it needs that. It kind of plays more like a tempo deck that uses Vantress Gargoyle and Hall of Storm Giants as beaters since they are cheap and easy to protect. Vantress Gargoyle can also be easily reanimated. Admittedly this deck can be a bit slow, and despite the fact that I described it as a tempo deck, it doesn't mainboard any x for 1s like Languish. 1 for 1s work extremely well when you have no large bombs and have one of the best draw spells. This strategy does make it incredibly hard to play, as you will undoubtebly realize after you play this deck a couple times. When Lurrus of the Dream-Den was legal I would mainboard Languish or Inquisition of Kozilek over [[Call of the Death-Dweller] because I didn't need Call of the Death-Dweller to reanimate the rogues. Inquisition of Kozilek is a great way to deal with threats that you may not necessarily have answers to, like Relic of Progenitus or Blood Moon, which also happens to be the hardest counter to this deck since Archmage's Charm forces you to run a very greedy manabase. One big advantage of Archmage's Charm that is easy to forget about is the third mode can be extremely good against token decks, and it makes your matchup against Dark Depths really easy. The reason Inquisition of Kozilek isn't in the mainboard despite it being one of the most efficient 1 for 1s is because it is very limited in it's targets in comparison to Thoughtseize. If you have the money for Thoughtseize, feel free to mainboard it. If you are playing this on Arena, you can run Lurrus of the Dream-Den because it isn't banned in Historic. I personally run Thoughtseize over Call of the Death-Dweller.