That raises some questions for me.
Assuming that the keys are located in Bastion, Maldraxxus, Ardenweald and Revendreth, with their respective leaders.
What about the Revendreth key? If the Eternal ones got the keys, like Kyrestia had one, who got the Revendreth key? Because if Denathrius got one, he could have given the key already to Zovaal.
Does that also mean, that the whole Primus = Runecarver thing is also wrong. Zovaal could have taken the key from his prisoner long time ago.
There is also the possibility of a key in Oribos, with the Arbiter.
What do you guys think?