Turn 1 Win, Soul Cauldron (Magic Arena Historic, Wilds of Eldraine)

Start with any Leyline on the battlefield
Play a Land
Cast Fragment Reality (only creature in library with mana value 3 or less is Birgi, which generates mana when you cast spells)
Cast Mox Amber
Cast Faithless Looting to put a Griselbrand into the graveyard
Cast Agatha's Soul Cauldron
Exile Griselbrand with Cauldron to give Birgi the activated ability of Griselbrand.
Draw 14 more cards and win (shown here: Fists of Flame plus Thud)

Bonus: Academic Dispute (the "learn" ability can discard a card from your hand, a backup plan if you don't have Faithless Looting) can get from sideboard Environmental Sciences, which gains 2 life so that you can draw 7 a third time.

If you win game one: Griselbrand is a two-card combo with Queza, Augur of Agonies. So, try and hard cast both, or use Cauldron as above.

Decklist:
2 Tormod's Crypt (M21) 241
4 Fragment Reality (Y22) 4
4 Mox Amber (DAR) 224
3 Leyline of Abundance (M20) 179
4 Thud (M19) 163
4 Leyline of Anticipation (M20) 64
4 Leyline of Sanctity (M20) 26
1 Birgi, God of Storytelling (KHM) 123
4 Fists of Flame (MH1) 123
4 Academic Dispute (STX) 91
4 Faithless Looting (STA) 38
1 Leyline of the Void (M20) 107
4 Agatha's Soul Cauldron (WOE) 242
4 Griselbrand (SIS) 31
1 Claim the Firstborn (ELD) 118
1 Seachrome Coast (ONE) 258
4 Inspiring Vantage (KLR) 283
3 Plains (WOE) 268
4 Needleverge Pathway (ZNR) 263

Sideboard
1 Environmental Sciences (STX) 1
4 A-Queza, Augur of Agonies (SNC) 212
1 Swamp (WOE) 271
1 Island (WOE) 269
4 Raffine's Tower (SNC) 254
4 Xander's Lounge (SNC) 260