Dammit; got Horatio down to 1000 HP before running out of resources. Had a Paladin of Dracul with 124 damage per hit, pendent of health, and a few levels accrued with dwarven gauntlets. All blood pools and potions saved for Horatio, as well as using an item from a previous floor to put 3 layers of corrosion on him. If I'd had BYSSEPS, Martyr Wraps, Platemail, or Whurrgarbl I would have been able to pull it off
Race was human. Had HALPMEH, Fine Sword, Dwarven Gauntlets, Spoon, and Yang's Sword in my inventory for the final battle (all other glyphs converted; no cash remaining, about a dozen tiles available to explore)
Boon selection was: Blood Hunger (x1), Blood Shield, Blood Tithe (x3), several Blood Swells. I had 4 layers of corrosion from one of the statues on a higher floor (weakening cured with fortitude tonic), but that was it.
So
definitely doable, but you need BYSSEPS or some form of accumulating damage bonus on damage reduction.