[Baalz]

Some spells that it might be worth taking into consideration for your pretender:

flaming arrows
darkness
army of lead
master enslave
fog warriors/mass flight/storm & wrathful skies (you get them all for the same price)

The key thing is these are all spells which under the right circumstances greatly amplify your power - particularly if they synergize with your other research goals and you can get them early. I wouldn't design my pretender solely to cast one spell, but I definitely take those into consideration when I'm deciding what paths my pretender needs and what spells would make a big difference for the nation I'm playing. For example, as I mention in my Marverni guide having flaming arrows is a great way to get that nation through the dangerous stage before their druids start laying the smack down, whereas army of lead is just *EVIL* for LA Ermor.