Tentative RTR standard legal deck. Idea from here.
The goal is to get out Axebane Guardian soulbonded to Galvanic Alchemist, along with three other creatures with Defender to reach infinite mana. The win condition is an Increasing Confusion for infinite to mill the opponent.
The earliest you can combo off is turn four:
Turn 1: Forest, Arbor Elf.
Turn 2: Land, Axebane Guardian.
Turn 4: Infinite mana, Increasing Confusion.
Tracker's Instincts is here to filter for the creatures you need to pull off the combo. As an additional bonus, Tracker's Instincts can drop an Increasing Confusion into the graveyard for you to cast for the flashback cost.