Eternal Card Game

The card required is the Weary Spiteling card which is a Rare Shadow Unit that cost 1 influence and is a wisp. The card has Entomb: +2/+2 and Flying. In order to get the achievement, the card must be played when it is at least 10/10. This means buffing it on the field will not count.

I went with a Shadow/Fire Deck since there are cards to sacrifice creatures in both factions.
The following are the cards I already had with no crafting to make a deck.

Units:
4x Scrap Hound (For Sacrifice Effect)
1x Weary Spiteling (Already had 1. The more the better. I didn't want to waste 800+ to craft)
3x Dark Wisp (For Draw)
1x Champion of Chaos (For Defense)
4x Ravenous Thornbeast (For Sacrifice Effect)
1x Soulbringer (Plays Wisp from the void)
2x Direwood Prowler (Sacrifice and Draw Effects)
1x Repulsive Gorger (Sacrifice and -1/-1 Effect Against Units)

Attachments:
3x Secret Passages (Sacrifice Effect)
1x Combustion Cell (Sacrifice Effect)
4x Ornate Katana (for Defense and Draw)
1x Dramatist's Mask (For Sacrifice and to cheat out other units)

Spells:
4x Combust (For Sacrifice and Killing Enemy Units)
4x Dark Return (Draw Units from the Void)
3x Cull the Deck (for Draw)
4x Devour (Sacrifice and Draw and Life Gain)
4x Quarry (for Draw)
3x Burn Out (for Killing Enemy Units)
2x Grasping at Shadows (Play units from the void)

Power:
11x Fire Sigil
14x Shadow Sigil

This can be done in the Gauntlet Mode where you versus AI. The plan is to draw Weary Spiteling, sacrifice it and either play it from the void or draw it. Dark Return will reduce the amount of times you need to draw/play from the void. The ideal setup is to have Secret Passage and Weary Spiteling on the field and Dark Returns in hand. All three cards cost 1 influence which means you quickly strengthen the creature and use it for defense.