Childe’s foul legacy is draining his life, Zhongli asks him not do use them, he doesn’t want to see Childe die, but Childe refuses, he’s a Fatui and he will need it for battles and missions.
“Unless you make a contract with me, sensei.” Childe smiles.
“And what do you want from me?”
“Make me yours.”
During the contract, they are bond as lovers. Childe keeps his promise, till the last moment of his life, he never uses the foul legacy again.

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