Just as good as the Carnivorous Strain, except for treacheries. Just need as much growth as the shroud where you stand and you are now immune to treachery effects. Between the 1-2 Uncanny Growths (in case you held it over from last turn) and Pathfinders/Shortcuts from being Seeker, this is a trivial task. Never mind that you can use it on any investigator no matter where they are!

You barely have to play the game with this thing. At the very least the cost of drawing Uncanny Growth should be an action like on the base unidentified version.

Surely this will get taboo'd pretty quickly. It is not hard to use cards like Breach the Door or Skeleton Key to reduce a location's shroud to zero. Add in Seeker movement tricks to allow investigators to end their turn there and on small maps it means no mythos phase, ever, for anyone.