Endgame - Expedition and Abyss interactions

When using both the expedition and abyss tablets in the endgame you can get a peculiar scenario where the expedition spawns over the abyss lines. When you go back to execute the expedition it can unearth mobs that are from the abyss monster pool (specifically I see a lot of the snake looking ones) along with the runic monsters. Sometimes these abyss snake-like monsters are not damageable, similar to an interaction that happens in the Abyssal Depths.