I never read the original story. The problem is Baron Sengir died as a child, became a vampire, and 'grew up' into his current appearance, right? That is pretty weird.
Yep. I actually thought I'd posted a link to the thread in the OP where I explained it in more detail, but it turns out I got my own walls of text mixed up and posted the wrong link, sorry...
Here's the correct one:
viewtopic.php?f=18&t=21707The most glaring problem with 'Song for the Plague Rats' is, to make it short, the fact that the Baron is still a child when he is turned into a vampire, and the story itself suggests that that's never going to change. When the boy talks about his father's plans to turn himself into a vampire, he explains: "It means he's going to change himself, so he won't get old - well, get any older anyway. He's going to make himself live forever." (p. 60). When they overpower his father and kill him in the process, this results in the boy being afflicted by the curse his father was going to put onto himself, and he declares himself the new Baron Sengir.
So, yeah, the story itself acknowledges that the vampiric condition would stop people from aging.
I do think vampires in some fiction continue aging, just as a slow rate and often becoming something more monstrous rather than just an old human. But that's different from a vampire that looks like a child going through an aging up process like living humans do.
Is it confirmed that Baron Sengir died and that his type of vampire is a post-mortem transformation? Or could he be transformed by the curse, so he is still 'living' or some semblance of it and so he continues aging?
Sengir vampires have indeed confirmed to be undead, though I can't tell you what exactly the sources for that were from the top of my head (or whether the short story in question brings it up). I'll try to find more info about it, though. Also note that the flavour text of the new card reads:
"Death is a small price to pay for immortality." - Baron SengirSo the card that appears to show him as a child being transformed into a vampire suggests he actually died an returned. There are vampires in Magic that
do age, but those are exactly the ones that aren't undead, namely those from Innistrad and Zendikar.