This deck is designed to make building a collection easier when starting out with a fresh Arena account. It won't get you to Mythic rank, but should be good enough to rack up daily/weekly wins and consistently reach Platinum. It's an aggro deck because ending games quickly means collecting wins quickly. The choice of Explorer/Pioneer format is for stability - it will never rotate out, nor get nerfed by digital rebalances.
Most importantly, the deck can be crafted without spending any money, using only wildcards from free packs. By entering all redeemable codes, you will end up with 66 packs. Opening them guarantees you 11 Uncommon wildcards, 9 Rares, and 2 Mythic Rares. Random-chance wildcards within the packs, while less guaranteed, are likely to give you another 22 Commons, 13 Uncommons, 1 Rare, and 1 Mythic, for a total of 22C/24U/10R/3M. Crafting this deck costs 10 Commons, 16 Uncommons, 9 Rares, and 2 Mythics.
If you find yourself with extra Rares and want to make this deck more competitive, I recommend focusing on lands. Monored means you don't have to worry about color-fixing, but it's still worth it to replace basic Mountains with multiple Den of the Bugbear, 1 Castle Embereth, 1 Nykthos, Shrine to Nyx, and 1 Sokenzan, Crucible of Defiance. The deck also doesn't mind Ramunap Ruins.
If you find yourself with extra Mythic Rares, consider Robber of the Rich or additional copies of Embercleave.
