I want to ambush my players with one of these when they leave the arctic town they're in

Quote from Vaetor_Tanner >>

I imagine these guys hunting style much like jumping spiders except their "jump" is the ethereal jaunt. Jumping spiders don't create elaborate webs designed to ensnare prey, instead they use their webs as anchors when jumping off things or to minimize risk of being blown away. Phase spiders could do the same by attaching a special web to anchor them to the material or ethereal plane. While it doesn't give them any extra abilities, it does give them just a bit more flavor for how they actually work. It could also be a weakness against a creature that can somehow see the web through truesight or something. Maybe the anchor can be severed to cause the creature to lose its ability to return in the spot they want or even flinging the creature off into the ether. Just an idea. 

As for the webwalker trait, I think its there so they can be used with other spiders that do spin web lairs so there's already webs around or just let them spin a web lair themselves. Just because they don't use the webs to trap prey in combat doesn't mean they can't have sticky lairs. 

I think that if they can use Ethereal Jaunt and bring their prey, then they could hunt by bringing unsuspecting prey into a web in the Ethereal Plane.

This boy is my wallpaper :) I love Phase Spiders.

I purchased one of these fellows from an exotic animal dealer. I am currently just out having fun

Fantastic! I, too, run for my kids, and that sounds like an exciting re-imagining of a classic monster. Good for you!

DMs, do your players use blink to avoid combat damage? Well have I got a monster for you...

this spiders ethereal jaunt is so annoying