The original thread doesn't say anything about time-traveling undead Zhentarim skymages.

However, it doesn't matter. As you say, both players and DMs can set parameters for their games. I have explained the parameters for the game I am running. Furthermore, I am announcing that no further exceptions to the allowable sources will be made, for anyone. You can have your own parameters for the games you play in. If my game meets those parameters, I invite you to craft a submission within the bounds I have described. If my game doesn't meet those parameters, feel free to reopen your thread and look for a DM who will. My only suggestion is that you explain those parameters up front so potential DMs know what you're asking for.