what does the 'just' in the clock mean?

The death of a god is judged and should it be just or heroic they shall remain lifeless.

Just means it was fair, it would be morally wrong for them to come back to life.  Basically, they deserved it or had it coming.

Example: Jane, she was doing bad things and died while doing them.  If she were to come back she would continue to be evil and that’s not good, therefore her death was just.