[@KatherinWinter]

They're like 4 times as fast as normal dogs, able to walk up walls and deform to slip through cracks and stuff like that, with a dog sense of smell, hearing, and keen ability to detect the supernatural. If you mean how far they can physically get from Curwen, as far as they like. [i]The Case of Charles Dexter Ward[/i] ended with a shade being called up essentially by accident and then going halfway round the world of its own accord to put down the rest of the antagonists.