I like how Durkon mentions that he should float up top…
Which, yeah, he should. And when he dies and the world isn’t destroyed, that vampire spirit is going to be cleaning latrines in Hel, second-guessing his decision making there 
This leads me to believe that this fight is going to be over very soon. Durkula isn’t going to get a chance to change his mind and go mistform to run out the clock.
Usingthis calculator, which I have probably misentered a value into and ignoring the green fire effect since I’m not sure what it would do, Roy would be hitting for 42 damage on a crit.
For a 14th level cleric at d8 HD, that’s a range of 14-112 HP (average of 63), but a vampire get d12 HD, so that’s 12-168 (average 91).
It’s not an instakill unless the green fire does something crazy like double-damage to undead and Durkula had a lot of bad rolls with his HD. Plus, as mentioned above, no Xs in the eyes.
EDIT: Not counting power attacks, which if he dumped a ton there Roy could be dealing 100+ damage in a blow.
I suspect that that has not been shown yet but will be answered afterwards.
Unless I’m missing something–which is entirely possible–undead aren’t subject to crits in 3.5 D&D. Something else must trigger the flashy effects.
I wonder if vampires get the Xs. According to RAW, a vampire that is reduced to 0 HP in combat automatically reverts to mist form (where it takes no further damage) and then has 2 hours to get back to its coffin before being destroyed automatically. I don’t know that Durkon has a coffin; if he does, it’s probably back on the airship. The only other vampire that we’ve seen in OotS, Malack, died in a more spectacular fashion of course.
Great catch!
I don’t think Durkon has a coffin. Malack commented on the need to get one when time permitted.
Oof! Right in the beard!
That** is** a critical hit to a dwarf.
Something weird’s going on with this particular time the sword’s turned green. Roy’s turned green this time too. Look at his eyes in this strip, compared to, say, the time he Great Cleaved all of the former Draketooth clan mummies, or when the sword caught fire fighting Sabine in Cliffport.
Simply lighting effect visual limitation or did Roy heal up on the strike too?
I like the fanwank as seen on the GITP forums that the green effect heals the wielder by the amount of damage dealt to the undead in question. Although it’s probably just an art effect.
I think this is the first time we’ve seen the green effect since the art upgrade, and I think it’s just from seeing Roy illuminated by the green light. Look at what it’s doing to his skin tone, too.
Hehe in closely scanning for details I may have missed, I noticed Roy’s scarf disappears in row 3 panel 2. Let’s read something into that. 
Even better, it reappears two panels later. Roy has a phasing scarf!
Plus, by this time Roy has received dozens of small hints including not incidentally Durkevil’s newly adopted speech patterns. His bad guy soliloquy in this strip sounds like someone that’s accessing another’s memories and is trying to hide it. And Roy has the intelligence to spot that, at least when bias and wishful thinking is overcome.
That said, nice catch.
I wonder: Durkula introduced himself to the other high priests as Durkon Thundershield, but Roy has now twigged - and announced - that he isn’t Durkon, so is Hel’s vote now invalid?
I wouldn’t think so. Vampires are typically named what they were in life, I suppose (not that there’s any rules). If he wants to call himself Durkon, then Durkon he is.
I’m just throwing this possibility out there again. Roy’s realization that Durkula is not just Durkon with an alignment change comes as he’s held up directly in front of the giant dwarf, made to look directly into his eyes as D works his evil mind control stuff.
Whatever, I’m looking forward to the next update!