Wei Wuxian barely makes a sound when Jin Zixun’s sword goes through his chest. A tiny noise is punched out of him — half gasp, half sigh. Jin Zixun, wearing that smirk that Lan Wangji has always hated, moves to pull the sword out. This won’t do; Lan Wangji knows enough about battlefield medicine to understand the principle of keeping the weapon in the wound until a medic arrives. So he does the only thing that occurs to him in the moment, letting the momentum of flight be the force behind the swing; he cuts off Jin Zixun’s hand. - Lan Wangji goes with Wei Wuxian to his nephew's one-month celebration instead of Wen Ning. They still don't make it to the party.