Master Yi, Wuju Bladesman

Master Yi, Wuju Bladesman gives a unit that defends alone +2 Might for free. Hold one battlefield with a single unit and spend  your cards and energy on the other. Never put a second unit on the battlefield you are holding: the moment two stand there, the  bonus is gone.

Mulligans: keep a two-cost unit (Pit Rookie or Lonely Poro), one trick (Punch First or En Garde) and Fiora, Peerless or Ambessa,  The Wolf. Send back a hand with two seven-costs or no unit under four energy.

Early game: Pit Rookie or Lonely Poro alone on one battlefield. A lone Poro defends as a 4 and draws a card when it dies. En  Garde gives +1, and +2 when your unit is alone.

Mid game: Fiora, Peerless doubles her Might one on one: alone on defence she is a 10, attacking the open battlefield she hits  for 6. Empower Ambessa, The Wolf with spare energy and she is a 7 that cannot be damaged  outside combat. Punch First is +5 at Action speed, so use it to win a fight you are already in. Guttural Roar is +4 on an  Empowered unit. Skyward Strike moves an enemy out of a fight, or stuns it at 6 XP.

Late game: Master Yi, Meditative becomes an 8 once you hold eight runes, and a 10 alone on defence. Stormclaw Ursine is a 6 with  Tank that channels a rune on arrival. Rampage removes the last blocker. Highlander is the insurance: the unit you choose comes  home instead of dying. Save it for Fiora, Ambessa or Meditative.

Mistakes to avoid: - Two units on one battlefield - Punch First to start a fight instead of finishing one - Highlander on a two-drop - Forgetting Twilight Shroud plays again from the trash