With the Halloween around the corner it's a perfect time for a new undead boss in the catacombs. The Vampire Lord can fly and has a cool superman-dash attack. He starts showing up in the catacombs after you find the Eye of Ramana.
Since the Vampire Lord is undead, you can use the Staff of the Dead to raise him from dead once you defeat him. He is a very powerful ally who can tank a lot of damage. His dash attack does massive damage to other bosses, so try to lure the boss enemies close to him when he's about to attack.
Happy Halloween!