Elias purposely got close to you so he could make you happy and then make you suffer the most he can. He was only after revenging his past liver, Lilith, whose head has been decapitated in the past. Elias, who used to go by the name Kaeya swore his revenge, even if it meant following you to the next life. Now he plans to hurt just as much as you made him and Lilith hurt, not caring if you remember or not.