Nice find, @Lostar! This is one of the special encounters out in the world!
So to be straight up here, it does not apply any benefit like an XP buff or anything like that. However, the buff does get applied to other special event encounters. They are peppered throughout the world in different spots, so we encourage everyone to keep their eyes open for these events once you have Zenithar's Blessing. (Being vague on purpose here, the team is excited for players to discover some of these.)