What do the Red Wizards of Thay, and particularly Rath Modar, want? [on hold]

I’m currently re-working a small Adventurers League module to insert into my campaign. It involves a Wizard of Thay secretly raising a decent-sized army of undead in the city’s catacombs without anyone noticing.

The original plot hook from the module is that they are trying to help Tiamat to break into the real world using said army of undead (in a convoluted, non-direct way, but still). But I have enough world-ending threats in my current campaign, so I want to change it to something more grounded, but something that still could be investigated by players for further play.

But… it’s hard to guess what Wizards of the Thay want? Especially their outcast — Rath Mogar, who the local zombie-raising wizard works for. Any good ideas for what they would possibly want in Neverwinter? Or at all?

Because I’m getting ideas with only something too generic, like “they are evil and want tons of zombies, duuuuh” and such.