Attacking Abby this turn actually looks like a good idea. Between unearthing the Grixis Slavedriver and casting Shallow Grave for the Pallid Mycoderm, you can force her to block with all her creatures and setting up a win on your next attack. The catch is that she’ll still get one more draw step to work with, and you’re not sure what’ll end up in her hand.
So perhaps you can win this turn. You’ll need a way to break through, however. That Dragon Shadow of yours is the likely ticket; you just need to get it on the right creature.
- Tap four plains to add
(three used as generic mana), and two swamps to add 
to your mana pool. - Spend
to cast Flicker on Death Pit Offering. Death Pit Offering leaves the battlefield, then returns to play under your control. - When Death Pit Offering enters the battlefield, its ability triggers. You sacrifice Keening Apparition, Undead Executioner, and Tribal Golem. All three cards and Dragon Shadow are put into your graveyard. You choose the order in which they are placed, so put Tribal Golem on top of Keening Apparition and Undead Executioner.
- When Undead Executioner dies, its ability triggers. Choose to have Abby’s Goblin Electromancer get -2/-2 until end of turn. The Electromander dies.
- Spend
to cast Grim Return on the Goblin Electromancer in Abby’s graveyard. Goblin Electromancer enters the battlefield under your control. - Spend to cast Shallow Grave. This lets you return Tribal Golem from your graveyard to the battlefield with haste. Because you control Goblin Electromancer (a goblin wizard), Tribal Golem has haste and flying. It is a 6/6 creature due to Death Pit Offering.
- When Tribal Golem enters the battlefield, Dragon Shadow’s ability triggers. Return Dragon Shadow from your graveyard to the battlefield attached to Tribal Golem (which is now a 7/6 creature with haste, flying and fear).
- Declare the start of your combat phase, assigning Tribal Golem to attack.
- Abby is unable to block Tribal Golem due to her lack of black or colorless flying creatures. Tribal Golem therefore deals 7 damage to Abby, defeating her.
