Okay, I think I have the basics of my character down.

His lair is underground, with huge facilities, research centres, hospitals for minions, etc. On the surface though, it looks like a medieval fort where the villain resides. He's an undead knight with a sword and shield.

Except he ain't good like a knight.

He might have a code of honour, challenging those deemed 'worthy' to one on one duels and waiting for those knocked down to get up to fight them, but he's still evil. His ultimate plan is world destruction. Or world domination. Or something.