I've been promising (or perhaps threatening?) this for a while now but I've now published the first ArM5 Mythos material here. There's a lot of fragments and concepts I'd like to explore that link into other sections but for the moment I've started in media res with some mechanics for the Elder Sign.
I've deliberately chosen to use cryptic branched line rather than the Derleth influenced pentagram with an eye style symbol.
Follow this link to the relevant article: The Elder Sign in Mythic Europe
I'll be running a poll shortly on which Mythos elements would seem easiest to adapt to Mythic Europe to create "Mythos Europe" or whatever soon.