Can normal army take out Sphinx pretender?

[Gargoyle]

I tried earlier to storm the Sphinx castle and "forgadabowdit". Eomer, Man and Ulm are the other powerful empires out there and are keeping my armies too occupied to bother with this "insignificant fool" (insert evil laughter).

He's bottled up in his fort. I think I will keep him there. I'm going to move my Pretender and Prophet (when I can have another since he died, lol) to the area and hope to drive down his dominion. I'd love to see him just fade away.