Whenever you take damage from another player, take the card that dealt it from the discard pile into your hand. A multi-card strike (like a Serpent Spear attack) hands you every card it used.
Lord only. When you need a Defense (against an Attack or Hail of Arrows), any living Wei-kingdom ally may play a Defense to answer it for you, asked in seat order until one provides it or all decline.
Cao Cao is a resilient anchor: every hit an enemy lands feeds his hand, so he can trade HP for cards and stay armed deep into the game. He is the natural Lord pick, with his guard skill letting Wei allies eat Attacks and Arrows for him; his weakness is being the table's top target, so lean on loyal teammates and don't bleed HP recklessly when no one can shield you.