First before reading this theory please watch Brofresco video of Jhin voice overs and give him your support he is an awesome player and funny one.https://youtu.be/ZfF7pTdrO68 Lets put some intersting facts first Jhins are legendary creatures that grant a person a wish. There are good Jhins and bad ones the good ones just grant you a wish while bad ones grant you a wish but at the cost of something.Usually Jhins are sealed inside something usually a lamp but it can be sealed in anything. 2nd fact from the voice overs we can conclude that Jhin is from ionia,ionia has many lores like yasuo,master yi,irelia and the Shen and Zed lore..Again from the voice overs we can say that he is involved in the Zed and Shen lore. Now lets get in the theory we know everything about Zed lore except why did Zed scream in the temple? And the truth behind the box that has the shadow techniques and why did the master let Zed go in the temple and try destory the box ( or kill what's inside it) and the master did not do it him self even before Zed learns the shadow techniques to prevent all the trouble from happening. From the voice overs Jhin admitted that Shen's father tried to censore him and seal his heart away so we can say Shen's father sealed Jhin's heart and probably inside a thing like a lamp and what's the only thing that probably was the lamp that Jhin was sealed in? YES THE BOX THAT HAD THE SHADOW TECHNIQUES. And from the voice over when Jhin said that his heart was sealed it means only his soul was sealed not his body. Now let's get more deep in the theory as i said earlier Jhins grant a wish and Jhin is an evil one so at the cost of something. Zed had a wish back thenbefore he had his powers he had a wish to beat Shen,So he went to the box(Jhin) and wished to be strong enough to beat Shen,And he had it but at the cost of Zed's humanity because after that he became an evil person and was banished. And what proves more that the box donot give shadow techniques but gives you a wish is that of it gives shadow techniques probably Shen's father the one who sealed Jhin at the first place was gonna have the same powers also. And Shen's father couldnot kill Jhin so he sealed his heart in the box. And the master thought that Zed was strong enough to go and destory the box ( kill Jhin) that's why Jhin tells Zed that he tried to kill him. But when Zed tried to kill Jhin Jhin appeared and shot Zed's eye that's why Zed screamed in the temple and he thought that the master had tricked him so he killed the master for pay back. And that's why Zed wore the mask after he killed the master. And probably Jhin shot Zed's to signfy dead eye and Jhin's name is dead eye as to say that "Dead eye was here" and that proves why Jhin shot Zed's eye on Zed's page cause Zed wanted to see again with his eye like sona wanted to talk again so she was shot in her throat. And that proves why Jhin claimed that Zed has tried to kill him. And after that Jhin's soul was relased and went in his body after Zed had tried to kill him and that explains why Jhin is free now. But still the reason why the master sealed Jhin is not yet proved . But hope you guys like it..