My opponent had the two key pieces to get started turn 2: Paradise Mantle (Equipped creature has ": Add one mana of any color to your mana pool." Equip ) on Blistercoil Weird (Whenever you cast an instant or sorcery spell, Blistercoil Weird gets +1/+1 until end of turn. Untap it.)
Keep tapping and untapping to generate mana and play cards that cost one mana in blue or red to cast and that allow you to draw a card each time (cantrips).
Three Peaks later, here is a 2-life zero-mana Gitaxian Probe.
Manamorphose does the same thing for 2 mana.
And then Pyromancer Ascension (Whenever you cast an instant or sorcery spell that has the same name as a card in your graveyard, you may put a quest counter on Pyromancer Ascension. Whenever you cast an instant or sorcery spell while Pyromancer Ascension has two or more quest counters on it, you may copy that spell. You may choose new targets for the copy.) begins the loop of more mana getting my opponent to draw more cards and once these land in the graveyard, they get more counters to copy those spells.
Hello Crimson Wisps, 1 counter on Pyromancer Ascension.
Enter Visions of Beyond.
Enter a second Faithless Looting (I skipped a few cards coming in).
And here Faithless Looting gets copied.
Now my opponent has a second Pyromancer Ascension. The copying can happen many times per turn.
My opponent has 22 cards in hand.
Grapeshot for the win.
And my opponent has an alternate winning condition with an 18/18 Blistercoil Weird unopposed.