Lan Wangji had never had call to perform the spell of silent communication before he and Wei Wuxian joined together to fight Xuanwu. He figured it was temporary. Spoiler alert: it wasn't. Or: the AU in which Lan Wangji and Wei Wuxian psychically bond in the cave, Wei Wuxian overhears Lan Wangji thinking about the fact that he actually likes him, and after several minutes of confusion, is fully on board with this.

The resentful energy occupying Wei Wuxian's body like an enemy army is very interested in giving him Lan Wangji, tied up with a bow. Wei Wuxian is hoping that Lan Wangji (who is far too noble and very keen to save Wei Wuxian's misguided soul) doesn't find out about any aspect of that.

Wei Wuxian almost does not catch the name of the song. In which the aftermath of the cave battle involves just enough communication to make a difference.

Aka Darth Talon, Arla Fett, and Xanatos break the timestream. It isn't the worst thing that could happen.