The two mazes start as far apart, they are slowly coming closer and closer and when they meet the player is crushed.
Nice mechanic have something similar developed in another area but in this case it is water filling in at the bottom while poison gas pumps in at the top and you need to solve the puzzle before you get floated into death
Unfortunately though one of the constraints of this particular location is that both mazes are basically static and your only real freedom beyond walking each maze is to port from one maze to the other and vice versa at a number of different locations. At the moment I am leaning to the idea of a monster on one maze's side which hunts for you when you traverse that maze and on the other maze a toxic environment which limits the amount of time you can spend up there and depending on how much time you spend there defines how much minimal recovery time you need on the monster's maze.
But I am very much open to suggestions improvements or more ideas