Origin of Slavian's magic and its meaning

"I think we reached the first checkpoint," Markus muttered silently under his nose. He then raised his head and looked at Layn. "What do you think, brother?" 

The entire expedition had extremely limited and most likely outdated information. The majority of what they knew about the terrain further away from the camp came from Sitra's and Layn's records of their return from the Slavian lands. And given how they traveled in a relatively straight lane, adding an overall complete lack of maps of the area, finding a correct path to any of their destinations proved to be a task far more challenging than initially expected. 

"I think I recall this place," Layn said, looking around patiently.