Stalker
From Arkham Horror Wiki
Stalkers are monsters that have a purple border instead of a normal black one.
Their normal movement speed in one space when their symbol is drawn on the Mythos Card.
Stalker will however, instead of moving along the arrow indicated on the card, attack any investigator that is within one space of them. They may use any movement line on the board, including ones that do not have movement arrows. They may not enter locations.
