The Arachnathid looks like a brownish-green scorpian, some people call it "Sand King" or simply "Scorp".
Along with Lacerti's, its most annoying ability is a sonic-rainboom, damaging and displacing anything in its charging path. After charging, it stops moving and takes a breath before continuing pursuing you.
If you outrun it, it will get bored and walk away for a few minutes.
Although it can climb cliffs, if you manuveur it around cliffs, it will occasionally break dance up and down the cliff several times before the pathing corrects itself.