I noticed that both smashing Globins into piles of meat and actually killing them both count as a kill when using Charm of the Vampire. This can be used to continually farm health. I also noticed that killing the flies spit out by the Duke of Flies do not appear to count as kills. Which events count towards Charm of the Vampire's ability and which don't? What enemies count as multiple kills?
All kills except for flies (both the harmless and aggressive flies) count towards charm of the vampire kills.
This includes splitting apart enemies that can be split (like The Fallen or Envy, but not the twin flies).
Each entity will count as one kill when depleted to 0 health. This means that for example, a Mr. Maw (being the fact that it's actually two entities combined into one enemy) will count as two kills when you fully kill it (even if you kill it while it's head is on its body). This also means that killing an enemy that splits into two upon death (like The Fallen) will count as 3 kills, one for the first enemy, and two for the second two.