They're rolling for what they might know about Vingilot, Maegnas Spiderbane, and The Nothing. Some might know one, some another, some more likely than others.
In Arkesh’s group, as I posted before, I’m looking for a roll from the Margravine about The Nothing. I guess it’s possible for Skellum to have heard of The Nothing, but much less likely.
It’s possible for Throisar to have heard something of Vingilot, or Maegnas Spiderbane, a long shot but not impossible.
Bane… considering where he’s from, none of the above.
Gleron … is well connected and at a nexus of information flow, so there is some chance he’s run across any particular piece of lore; a small chance in this case, for having heard of any of the three. Likewise, Bracken Jorden is very well traveled and has a small chance.
So: Gleron, Bracken, Throisar, join the roll-fest. Knowledge Planes, or whatever else you might think is applicable. If you have ranks in Sailing, add them as a bonus. You’re now within The PlanTM so +2 Luck. There are some Morale bonuses they have floating around, but you’re not close enough yet to be in range. And, a percentile roll, 1d100+2 which counts the +2 Luck for that too.