I have been contacted to write the script of a play. Is it permissible for me to write a play in which there are many non Muslim characters? There will be no display of shirk or any rituals of other religions. I should also mention that the script I have come up with includes a king who does not rule by the sharia. The king is presented in a negative light but that is not because of not adhering to the sharia but because of his pride and greed. There is no mention or reference to Islam or the shariah law.
I would edit your question to end with "Please, brothers and sisters, I need an urgent answer".
Onto the answer. First of all, the default in Islam is that anything that is not forbidden is allowed. Writing a play with a pure heart (niya safia) with no purpose of calling to that which is unholy (makrouh) is absolutely fine. Your play doesn't have to preach, Islam does not forbid any act of art unless it contains Sharia, I am frankly perplexed by the question.
Go ahead, write your play!