Damage dealt to a creature by a source with wither and/or infect causes that sources controller to put that many -1/-1 counters on that creature
Dual lands are expensive due to high demand, limited supply, and power level
If all you want is to find one card you can find it but the Vault offers something more by letting you preview what cards would come along with it, allowing players to plot out the next several turns of the game and see if the sequence being offered would get it done
For such a linear strategy, and reliance on small, often lower-power level cards, I give this a low-power level ranking
2-color decks are strictly two colors, not a single card with a third
By combining early game ramp with cost-reducers like Dragonspeaker Shaman and Dragonlord's Servant, you will accelerate into terrifying aerial threats like Atarka, World Render and Drakuseth, Maw of Flames