As you access the familiar locus of arcane power; you become immediately aware that something has gone horribly wrong.
The ley lines - you can still sense their presence, but they are obfuscated and sticky as if veiled by the strands of a spider's web.
Worse, you can sense something more. Beyond the web, the pulsating life force of another world swells against the walls of an unseen dimension, threatening to burst through into your own.
If Atlach-Nacha is not the Ancient One, place the Web Between Worlds Rumor Mythos card in play with 4 Eldritch Tokens on it.