Hello, Lord!

You can complete the quest by purchasing units at your Black Market. Or you will need to collect Scrolls to unlock the units.

dliard55 said:

I keep getting the same Mar'eth quest of training 7 warlocks every day.  Which would be fine if I could train them, but since I don't even have Great Lords discovered on that particular game, this is mission impossible with a vengeance.  Something needs to be done about how these quests are assigned, otherwise they will get ignored.

Hello :)

Not all Quests can be easily completed at once. For some of them, you need to develop your Castle and make some discoveries done.

This Quest is one of them. As Pavel said, you can also complete this Quest by purchasing Units on the Black Market.