I can think of two depictions of someone locked into place like this on film. One is the three-eyed raven in Game of Thrones, who has grown into the tree and been entangled with it. Clearly, he cannot physically move, but from there, he can see any time or any place. The other is the villain Father in Fullmetal Alchemist, who attaches to his chair and draws in whatever is flowing through the pipes surrounding it. He can (and does) stand up and leave the throne, but the implication is that he can control things from there and doesn't need to very often.
So basically, if we want to depict some sort of viney connection to the throne that rips out the roots when he stands, we can, so long as we are emphasizing how that gives him control.