[Cainehill]

Alternatively, while I understand why you want him with the assault army, I'd probably set him in a laboratory that early. Turn 4, you don't have any decent spells researched for him to cast.

Also, I'm not positive - but I got the impression he can cause disease to troops in the same province with him, without having to get next to them on the battlefield.

So - I give him a nice province with a lab all to himself, and have him research and/or summon enough undead until he has his own army to fight with.