I have a copy of Krenko and a Serra Avenger with what looks to be extra bolded title text, is there any extra value in the misprint here?

I have a Serra Avenger which looks just like you describe. I asked The Misprint Guy via Reddit if he had seen ink smudging on M13 cards and he did say that the set has many more small printing errors than other sets.

Here's a picture of the Krenko and the Avenger.

The Groundseal is normal text.

Not really. The only time a misprint is usually worth more is if you can see the name of another card in it. These are what brings in money. especially the miscut dragon in the bottom left.

drgolovacroxby wrote:Not really. The only time a misprint is usually worth more is if you can see the name of another card in it. These are what brings in money. especially the miscut dragon in the bottom left.

That's not actually a dragon, it's an Avatar of Fury.

On a related note, I should probably take a closer look at a Mirror Entity I have that has some smeared text...