Phase spider

A phase spider is a magical beast akin to a predaceous version of the ethereal filcher.

Description
The phase spider resembles a giant, two eyed, spindly legged spider with the same dark green and white coloration of an ethereal filcher (though it is a bit more blue than green). While the filcher transports between the Ethereal Plane and the Material Plane for the purpose of stealing, the phase spider does this for the purpose of hunting. It looks for a likely spot in the Ethereal Plane, and then teleports (its form of teleportation is known as "phasing," hence the name) to the Material Plane, presumably ambushing travelers it expected to be there, bites and kills them, and then quickly retreats back to the Ethereal Plane.

They cannot speak, being animals.

They are regarded as neutral in alignment.