Deckbuilder's Challenge LX: Dominaria Hat-trick

Oh yeah. I know exactly what I will do.

This bizarre number of a deck aims to try and aggressively mulligan via Serum Powder into Leyline of Singularity to choke out the opponent's early game as much as possible (especially for aggro decks, who are likely running 4xs of various efficient little critters) while we use Robaran Mercenaries to try and now clone our so called 'Legendary' Mercs and their various activated abilities - for example, we can play Seahunter and tutor out both Morphon, the Boundless and Chameleon Colossus out on the next turn, or double up with Rathi Assassin to destroy what few creatures our opponent does manage to squeeze out. Black Market Connections and Jedit Ojanen, Mercenary act as alternate means of letting us go wide and we use a mixed package of Oblivion Ring, Temporary Lockdown to remove other threats as best as we can while Moon-Blessed Cleric acts as another body on the field that we can use up to tutor any other key cards or removal. Naturally, we use 4x Cateran Summons to try and get the best Merc for any given situation.

Since this is a fairly janky deck that relies on a comically overcomplicated combo, our sideboard is mostly filled with more straightfoward Mercenaries like Mercenary Knight and Skulking Fugitive to let us try and transform our deck into a more traditional beatdown deck in a pinch, or replace one of the combos for the Robaran package with 4x Counterspell if we suspect it's better to lean into our control enchantments package and slowly work our way to a powerful single creature like Morophon or Chameleon Colossus that can close out the game.