Void infiltration into Runeterra.
The entrance of Rek'sai into League lore has brought kind of an interesting look at the void infiltration. Previously most of our contact with The Void has been specific characters with an active role in infiltration. There have been hints of lower levels of "troop", or even varying motives(consumption with Cho and Kog vs studying with Vel'koz). But Rek'sai and even more specifically the xer'sai in general bring on another facet.
The Xer'sai(I'm not sure whether to capitalize that) have basically insinuated themselves into the ecology of Shurima. They are now a part of that region. And not an uncommon part(in the deeper reaches anyways) from what the lore explains. It makes me wonder how far this goes and if there are other subtle or not so subtle invasions at the ecological level in Runeterra. Or perhaps small outposts of Void taken areas.
It reminds me somewhat of the Chtorr series by David Gerrold if anyone has ever read that.